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Dayton, Ohio

Dayton is a city in Montgomery and Greene counties and the county seat of Montgomery County, Ohio, United States. As of the 2020 census, the city proper had a population of 137,644, making it the sixth-most populous city in Ohio. It anchors the state's fourth-largest metropolitan area, the Dayton metropolitan area, which had 814,049 residents. Dayton is located within Ohio's Miami Valley region, 50 mi north of Cincinnati and 60 mi west of Columbus.

Dayton was founded in 1796 along the Great Miami River and named after Jonathan Dayton, a Founding Father who owned a significant amount of land in the area. It grew in the 19th century as a canal town and was home to many patents and inventors, most notably the Wright brothers, who developed the first successful motor-operated airplane. It later developed an industrialized economy and was home to the Dayton Project, a branch of the larger Manhattan Project, to develop polonium triggers used in early atomic bombs. With the decline of heavy manufacturing in the late 20th century, Dayton's businesses have diversified into a service economy.

Ohio's borders are within 500 mi of roughly 60 percent of the country's population and manufacturing infrastructure, making Dayton a logistics hub. The city is home to Wright-Patterson Air Force Base, a significant contributor to research and development in the industrial, aeronautical, and astronautical engineering fields. Along with defense and aerospace, healthcare accounts for much of the Dayton area's economy. Significant institutions in Dayton include the Air Force Institute of Technology, Carillon Historical Park, Dayton Art Institute, Dayton Performing Arts Alliance, National Museum of the United States Air Force, and University of Dayton.

History
Dayton was founded on April 1, 1796, by 12 settlers known as the Thompson Party. They traveled in March from Cincinnati up the Great Miami River by pirogue and landed at what is now St. Clair Street, where they found two small camps of Native Americans. Among the Thompson Party was Benjamin Van Cleve, whose memoirs provide insights into the Ohio Valley's history. Two other groups traveling overland arrived several days later. The oldest surviving building is Newcom Tavern, which was used for various purposes, including housing Dayton's first church, which is still in existence.

In 1797, Daniel C. Cooper laid out Mad River Road, the first overland connection between Cincinnati and Dayton, opening the "Mad River Country" to settlement. Ohio was admitted into the Union in 1803, and the village of Dayton was incorporated in 1805 and chartered as a city in 1841. The city was named after Jonathan Dayton, a captain in the American Revolutionary War who signed the U.S. Constitution and owned a significant amount of land in the area. In 1827, construction on the Dayton–Cincinnati canal began, which provided a better way to transport goods from Dayton to Cincinnati and contributed significantly to Dayton's economic growth during the 1800s.

Innovation

Innovation led to business growth in the region. In 1884, John Henry Patterson acquired James Ritty's National Manufacturing Company along with his cash register patents and formed the National Cash Register Company (NCR). The company manufactured the first mechanical cash registers and played a crucial role in the shaping of Dayton's reputation as an epicenter for manufacturing in the early 1900s. In 1906, Charles F. Kettering, a leading engineer at the company, helped develop the first electric cash register, which propelled NCR into the national spotlight. NCR also helped develop the US Navy Bombe, a code-breaking machine that helped crack the Enigma machine cipher during World War II.

Dayton has been the home for many patents and inventions since the 1870s. According to the National Park Service, citing information from the U.S. Patent Office, Dayton had granted more patents per capita than any other U.S. city in 1890 and ranked fifth in the nation as early as 1870. The Wright brothers, inventors of the airplane, and Charles F. Kettering, world-renowned for his numerous inventions, hailed from Dayton. The city was also home to James Ritty's Incorruptible Cashier, the first mechanical cash register, and Arthur E. Morgan's hydraulic jump, a flood prevention mechanism that helped pioneer hydraulic engineering. Paul Laurence Dunbar, an African-American poet and novelist, penned his most famous works in the late 19th century and became an integral part of the city's history.

Birthplace of aviation
Powered aviation began in Dayton. Orville and Wilbur Wright were the first to construct and demonstrate powered flight. Although the first flight was in Kitty Hawk, North Carolina, their Wright Flyer was built in and returned to Dayton for improvements and further flights at Huffman Field, a cow pasture 8 mi northeast of Dayton, near the current Wright-Patterson Air Force Base.

When the government tried to move development to Langley field in southern Virginia, six Dayton businessmen including Edward A. Deeds, formed the Dayton-Wright Airplane Company in Moraine and established a flying field. Deeds also opened a field to the north in the flood plain of the Great Miami River between the confluences of that river, the Stillwater River, and the Mad River, near downtown Dayton. Later named McCook Field for Alexander McDowell McCook, an American Civil War general, this became the Army Signal Corps' primary aviation research and training location. Wilbur Wright also purchased land near Huffman prairie to continue their research.

During World War I, the Army purchased 40 acres adjacent to Huffman Prairie for the Fairfield Aviation General Supply Depot. As airplanes developed more capability, they needed more runway space than McCook could offer, and a new location was sought. The Patterson family formed the Dayton Air Service Committee, Inc which held a campaign that raised $425,000 in two days and purchased 4,520.47 acre northeast of Dayton, including Wilbur Wright Field and the Huffman Prairie Flying Field. Wright Field was "formally dedicated" on October 12, 1927. After World War II, Wright Field and the adjacent Patterson Field, Dayton Army Air Field, and Clinton Army Air Field were merged as the Headquarters, Air Force Technical Base. On January 13, 1948, the facility was renamed Wright-Patterson Air Force Base.

Great Dayton Flood
A catastrophic flood in March 1913, known as the Great Dayton Flood, led to the creation of the Miami Conservancy District, a series of dams as well as hydraulic pumps installed around Dayton, in 1914.

The war effort
Like other cities across the country, Dayton was heavily involved in the war effort during World War II. Several locations around the city hosted the Dayton Project, a branch of the larger Manhattan Project, to develop polonium triggers used in early atomic bombs. The war efforts led to a manufacturing boom throughout the city, including high-demand for housing and other services. At one point, emergency housing was put into place due to a housing shortage in the region, much of which is still in use today.

Alan Turing is widely considered to be the father of theoretical computer science and artificial intelligence. He visited the National Cash Register (NCR) company in Dayton in December 1942. He was able to show that it was not necessary to build 336 Bombes, so the initial order was scaled down to 96 machines to decipher German Enigma-machine-encrypted secret messages during World War II.

Post-war Dayton
Between the 1940s and the 1970s, the city saw significant growth in suburban areas from population migration. Veterans were returning from military service in large numbers seeking industrial and manufacturing jobs, a part of the local industry that was expanding rapidly. Advancements in architecture also contributed to the suburban boom. New, modernized shopping centers and the Interstate Highway System allowed workers to commute greater distances and families to live further from the downtown area. More than 127,000 homes were built in Montgomery County during the 1950s.

During this time, the city was the site of several race riots, including one in 1955 following the murder of Emmett Till, the 1966 Dayton race riot, two in 1967 (following a speech by civil rights activist H. Rap Brown and another following the police killing of an African American man), and one in 1968 as part of the nationwide King assassination riots.

Since the 1980s, however, Dayton's population has declined, mainly due to the loss of manufacturing jobs and decentralization of metropolitan areas, as well as the national housing crisis that began in 2008. While much of the state has suffered for similar reasons, the impact on Dayton has been greater than most. Dayton had the third-greatest percentage loss of population in the state since the 1980s, behind Cleveland and Youngstown. Despite this, Dayton has begun diversifying its workforce from manufacturing into other growing sectors such as healthcare and education.

Peace accords
In 1995, the Dayton Agreement, a peace accord between the parties to the hostilities of the conflict in Bosnia-Herzegovina and the former Yugoslavia, was negotiated at Wright-Patterson Air Force Base, near Fairborn, Ohio, from November 1 to 21.

Richard Holbrooke wrote about these events in his memoirs:

"There was also a real Dayton out there, a charming Ohio city, famous as the birthplace of the Wright brothers. Its citizens energized us from the outset. Unlike the population of, say, New York City, Geneva or Washington, which would scarcely notice another conference, Daytonians were proud to be part of history. Large signs at the commercial airport hailed Dayton as the 'temporary center of international peace.' The local newspapers and television stations covered the story from every angle, drawing the people deeper into the proceedings. When we ventured into a restaurant or a shopping center downtown, people crowded around, saying that they were praying for us. Warren Christopher was given at least one standing ovation in a restaurant. Families on the airbase placed 'candles of peace' in their front windows, and people gathered in peace vigils outside the base. One day they formed a 'peace chain,' although it was not large enough to surround the sprawling eight-thousand-acre base. Ohio's famous ethnic diversity was on display."

2000s initiatives
Downtown expansion that began in the 2000s has helped revitalize the city and encourage growth. Day Air Ballpark, home of the Dayton Dragons, was built in 2000. The highly successful minor league baseball team has been an integral part of Dayton's culture. In 2001, the city's public park system, Five Rivers MetroParks, built RiverScape MetroPark, an outdoor entertainment venue that attracts more than 400,000 visitors each year. A new performance arts theater, the Schuster Center, opened in 2003. A large health network in the region, Premier Health Partners, expanded its Miami Valley Hospital with a 12-story tower addition.

In 2010, the Downtown Dayton Partnership, in cooperation with the City of Dayton and community leaders, introduced the Greater Downtown Dayton Plan. It focuses on job creation and retention, infrastructure improvements, housing, recreation, and collaboration. The plan is to be implemented through the year 2020.

Nicknames

Dayton is known as the "Gem City". The nickname's origin is uncertain, but several theories exist. In the early 19th century, a well-known racehorse named Gem hailed from Dayton. In 1845, an article published in the Cincinnati Daily Chronicle by an author known as T stated:

"In a small bend of the Great Miami River, with canals on the east and south, it can be fairly said, without infringing on the rights of others, that Dayton is the gem of all our interior towns. It possesses wealth, refinement, enterprise, and a beautiful country, beautifully developed."

In the late 1840s, Major William D. Bickham of the Dayton Journal began a campaign to nickname Dayton the "Gem City." The name was adopted by the city's Board of Trade several years later. Paul Laurence Dunbar referred to the nickname in his poem, "Toast to Dayton", as noted in the following excerpt:

She shall ever claim our duty, For she shines—the brightest gem That has ever decked with beauty Dear Ohio's diadem.

Dayton also plays a role in a nickname given to the state of Ohio, "Birthplace of Aviation." Dayton is the hometown of the Wright brothers, aviation pioneers who are credited with inventing and building the first practical airplane in history. After their first manned flights in Kitty Hawk, North Carolina, which they had chosen due to its ideal weather and climate conditions, the Wrights returned to Dayton and continued testing at nearby Huffman Prairie.

Additionally, Dayton is colloquially referred to as "Little Detroit". This nickname comes from Dayton's prominence as a Midwestern manufacturing center.

Geography
According to the United States Census Bureau, the city has a total area of 56.50 sqmi, of which 55.65 sqmi is land and 0.85 sqmi is water.

Climate
Dayton's climate features warm, muggy summers and cold, dry winters, and is classified as a humid continental climate (Köppen Dfa). Unless otherwise noted, all normal figures quoted within the text below are from the official climatology station, Dayton International Airport, at an elevation of 304.8 m about 10 mi to the north of downtown Dayton, which lies within the valley of the Miami River; thus temperatures there are typically cooler than in downtown.

At the airport, monthly mean temperatures range from 27.5 °F in January to 74.1 °F in July. The highest temperature ever recorded in Dayton was 108 °F on July 22, 1901, and the coldest was -28 °F on February 13 during the Great Blizzard of 1899. On average, there are 14 days of 90 °F+ highs and 4.5 nights of sub-0 °F lows annually. Snow is moderate, with a normal seasonal accumulation of 23.3 in, usually occurring from November to March, occasionally April, and rarely October. Precipitation averages 41.1 in annually, with total rainfall peaking in May.

Dayton is subject to severe weather typical of the Midwestern United States. Tornadoes are possible from the spring to the fall. Floods, blizzards, and severe thunderstorms can also occur.

On Memorial Day of 2019, Dayton suffered extensive property damage and one death during a tornado outbreak, in which a total of 15 tornadoes touched down in the Dayton area. Although some of the tornadoes were only EF0 and remained on the ground for less than a mile, one was an EF4 measuring a half-mile-wide (805 meters), which tore through the communities of Brookville, Trotwood, Dayton, Northridge, and Riverside. Several streets were closed, including portions of I-75 and North Dixie Drive in Northridge. 64,000 residents lost power and much of the region's water supply was cut off.

Ecology
The Dayton Audubon Society is the National Audubon Society's local chapter. The Dayton chapter manages local activities contributing to the annual, hemisphere-wide Christmas Bird Count. The Chapter began participation in the National Count in 1924. The local Count was initially coordinated by Ben Blincoe, who was succeeded by Jim Hill in 1970. In the mid-1960s, the freezing of Lake Erie and associated marshlands led species of waterfowl to appear in the Dayton-area, where surface waters remained unfrozen. Nine varieties of birds have been observed every year in the Dayton area: downy woodpecker, Carolina chickadee, tufted titmouse, brown creeper, cardinal, junco, tree sparrow, song sparrow and crow.

Architecture
Unlike many Midwestern cities its age, Dayton has very broad and straight downtown streets (generally two or three full lanes in each direction) that improved access to the downtown even after the automobile became popular. The main reason for the broad streets was that Dayton was a marketing and shipping center from its beginning; streets were broad to enable wagons drawn by teams of three to four pairs of oxen to turn around. Also, some of today's streets were once barge canals flanked by draw-paths.

A courthouse building was built in downtown Dayton in 1888 to supplement Dayton's original Neoclassical courthouse, which still stands. This second, "new" courthouse has since been replaced with new facilities as well as a park. The Old Court House has been a favored political campaign stop. On September 17, 1859, Abraham Lincoln delivered an address on its steps. Eight other presidents have visited the courthouse, either as presidents or during presidential campaigns: Andrew Johnson, James Garfield, John F. Kennedy, Lyndon B. Johnson, Richard Nixon, Gerald Ford, Ronald Reagan, and Bill Clinton.

The Dayton Arcade, which opened on March 3, 1904, was built in the hopes of replacing open-air markets throughout the city. Throughout the decades, the Arcade has gone through many transformations but has retained its charm. Some of its main features include a Flemish facade at the Third Street entrance, a glass dome above the Arcade rotunda, and a chateau roof line above the Third Street facade. The Dayton Arcade is currently under renovations with no official completion date set.

In 2009, the CareSource Management Group finished construction of a $55 million corporate headquarters in downtown Dayton. The 300000 sqft, 10-story building was downtown's first new office tower in more than a decade.

Dayton's two tallest buildings are the Kettering Tower at 408 ft and the KeyBank Tower at 385 ft. Kettering Tower was originally Winters Tower, the headquarters of Winters Bank. The building was renamed after Virginia Kettering when Winters was merged into Bank One. KeyBank Tower was known as the MeadWestvaco Tower before KeyBank gained naming rights to the building in 2008.

Ted Rall said in 2015 that over the last five decades Dayton has been demolishing some of its architecturally significant buildings to reduce the city's rental vacancy rate and thus increase the occupancy rate.

Neighborhoods
Dayton's ten historic neighborhoods—Oregon District, Wright Dunbar, Dayton View, Grafton Hill, McPherson Town, Webster Station, Huffman, Kenilworth, St. Anne's Hill, and South Park—feature mostly single-family houses and mansions in the Neoclassical, Jacobethan, Tudor Revival, English Gothic, Chateauesque, Craftsman, Queen Anne, Georgian Revival, Colonial Revival, Renaissance Revival Architecture, Shingle Style Architecture, Prairie, Mission Revival, Eastlake/Italianate, American Foursquare, and Federal styles. Downtown Dayton is also a large area that encompasses several neighborhoods itself and has seen a recent uplift and revival.

Suburbs
Dayton's suburbs with a population of 10,000 or more include Beavercreek, Centerville, Clayton, Englewood, Fairborn, Harrison Township, Huber Heights, Kettering, Miami Township, Miamisburg, Oakwood, Riverside, Springboro, Trotwood, Vandalia, Washington Township, West Carrollton, and Xenia.

In the federal government's National Urban Policy and New Community Development Act of 1970, funding was provided for thirteen "new towns" or planned cities throughout the country. One location was set to become a suburb of Dayton and was known variously as Brookwood or Newfields. The goal was to have an entirely new suburb that would eventually house about 35,000 residents. The new town was to be located between Trotwood and Brookville, and modeled on the ideas of Ian McHarg. The project was abandoned in 1978 and most of the land became Sycamore State Park.

Demographics
Dayton's city proper population declined significantly from a peak of 262,332 residents in 1960 to 137,644 residents in 2020. This was in part due to the slowdown of the region's manufacturing sector. The metropolitan area as a whole has experienced both population growth and decreases since 1960, with the overall trend leaning towards growth for the metro area. The city's most populous ethnic group, white, declined from 78.1% in 1960 to 51.7% by 2010.

2020 census
As of the census of 2020, there were 137,644 people living in the city, for a population density of 2,466.47 people per square mile (952.31/km2). There were 68,899 housing units. The racial makeup of the city (including Hispanics in the racial counts) was 47.6% White, 40.7% Black or African American, 0.4% Native American, 1.4% Asian, 0.1% Pacific Islander, 3.3% from some other race, and 6.6% from two or more races. Separately, 5.7% of the population were Hispanic or Latino of any race.

There were 63,308 households, out of which 22.1% had children under the age of 18 living with them, 24.5% were married couples living together, 30.9% had a male householder with no spouse present, and 38.2% had a female householder with no spouse present. 47.4% of all households were made up of individuals, and 14.6% were someone living alone who was 65 years of age or older. The average household size was 1.95, and the average family size was 2.83.

18.9% of the city's population were under the age of 18, 65.0% were 18 to 64, and 16.1% were 65 years of age or older. The median age was 38.4. For every 100 females, there were 101.5 males.

According to the U.S. Census American Community Survey, for the period 2016-2020 the estimated median annual income for a household in the city was $43,780, and the median income for a family was $60,408. About 25.4% of the population were living below the poverty line, including 39.5% of those under age 18 and 21.5% of those age 65 or over. About 53.6% of the population were employed, and 24.4% had a bachelor's degree or higher.

2010 census
As of the 2010 census, there were 141,759 people, 58,404 households, and 31,064 families residing in the city. The population density was 2543.2 PD/sqmi. There were 74,065 housing units at an average density of 1330.9 /sqmi. The racial makeup of the city was 51.7% White, 42.9% African American, 0.3% Native American, 0.9% Asian, 1.3% from other races, and 2.9% from two or more races. Hispanic or Latino residents of any race were 3.0% of the population.

There were 58,404 households, of which 28.3% had children under the age of 18 living with them, 25.9% were married couples living together, 21.4% had a female householder with no husband present, 5.9% had a male householder with no wife present, and 46.8% were non-families. 38.8% of all households were made up of individuals, and 11.2% had someone living alone who was 65 years of age or older. The average household size was 2.26, and the average family size was 3.03.

The median age in the city was 34.4 years. 22.9% of residents were under the age of 18; 14.2% were between the ages of 18 and 24; 25.3% were from 25 to 44; 25.8% were from 45 to 64, and 11.8% were 65 years of age or older. The gender makeup of the city was 48.7% male and 51.3% female.

Crime
Dayton's crime declined between 2003 and 2008 in key categories according to FBI Uniform Crime Reports and Dayton Police Department data. In 2009, crime continued to fall in the city of Dayton. Crime in the categories of forcible rape, aggravated assault, property crime, motor vehicle theft, robbery, burglary, theft and arson all showed declines for 2009. Overall, crime in Dayton dropped 40% over the previous year. The Dayton Police Department reported a total of 39 murders in 2016, which marked a 39.3% increase in homicides from 2015.

John Dillinger, a bank robber during the early 1930s, was captured and arrested by Dayton city police while visiting his girlfriend at a high-class boarding house in downtown Dayton.

On August 4, 2019, a mass shooting took place in Dayton. Ten people were killed, including the perpetrator, and twenty-seven were injured.

Economy
Dayton's economy is relatively diversified and vital to the overall economy of the state of Ohio. In 2008 and 2009, Site Selection magazine ranked Dayton the #1 medium-sized metropolitan area in the U.S. for economic development. Dayton is also among the top 100 metropolitan areas in both exports and export-related jobs, ranked 16 and 14 respectively by the Brookings Institution. The 2010 report placed the value of exports at $4.7 billion and the number of export-related jobs at 44,133. The Dayton Metropolitan Statistical Area ranks 4th in Ohio's Gross Domestic Product with a 2008 industry total of $33.78 billion. Additionally, Dayton ranks third among 11 major metropolitan areas in Ohio for exports to foreign countries. The Dayton Development Coalition is attempting to leverage the region's large water capacity, estimated to be 1.5 trillion gallons of renewable water aquifers, to attract new businesses. Moody's Investment Services revised Dayton's bond rating from A1 to the stronger rating of Aa2 as part of its global recalibration process. Standard & Poor's upgraded Dayton's rating from A+ to AA− in the summer of 2009.

Bloomberg Businessweek ranked Dayton in 2010 as one of the best places in the U.S. for college graduates looking for a job. Companies such as Reynolds and Reynolds, Stratacache, CareSource, DP&L (soon AES inc), LexisNexis, Kettering Health Network, Premier Health Partners, and Standard Register have their headquarters in Dayton. It is also the former home of the Speedwell Motor Car Company, MeadWestvaco (formerly known as the Mead Paper Company), and NCR. NCR was headquartered in Dayton for over 125 years and was a major innovator in computer technology.

Research and development
The Dayton region gave birth to aviation and is known for its high concentration of aerospace and aviation technology. In 2009, Governor Ted Strickland designated Dayton as Ohio's aerospace innovation hub, the state's first such technology hub. Two major United States research and development organizations have leveraged Dayton's historical leadership in aviation and maintain their headquarters in the area: The National Air and Space Intelligence Center (NASIC) and the Air Force Research Laboratory (AFRL). Both have their headquarters at Wright-Patterson Air Force Base.

Several research organizations support NASIC, AFRL, and the Dayton community. The Advanced Technical Intelligence Center is a confederation of government, academic, and industry partners. The University of Dayton Research Institute (UDRI) is led by the University of Dayton. The Cognitive Technologies Division (CTD) of Applied Research Associates, Inc., which carries out human-centered research and design, is headquartered in the Dayton suburb of Fairborn. The city of Dayton has started Tech Town, a development project to attract technology-based firms and revitalize the downtown area. Tech Town is home to the world's first RFID business incubator. The University of Dayton–led Institute for Development & Commercialization of Sensor Technologies (IDCAST) at TechTown is a center for remote sensing and sensing technology. It is one of Dayton's technology business incubators housed in The Entrepreneurs Center building.

Healthcare
The Kettering Health Network and Premier Health Partners have a major role on the Dayton area's economy. Hospitals in the Greater Dayton area have an estimated combined employment of nearly 32,000 and a yearly economic impact of $6.8 billion. In addition, several Dayton area hospitals consistently earn top national ranking and recognition including the U.S. News & World Report's list of "America's Best Hospitals" as well as many of HealthGrades top ratings. The most notable hospitals are Miami Valley Hospital and Kettering Medical Center.

The Dayton region has several key institutes and centers for health care. The Center for Tissue Regeneration and Engineering at Dayton focuses on the science and development of human tissue regeneration. The National Center for Medical Readiness (NCMR) is also in the Dayton area. The center includes Calamityville, which is a disaster training facility. Over five years, Calamityville is estimated to have a regional economic impact of $374 million. Also, the Neurological Institute at Miami Valley Hospital is an institute focused on the diagnosis, treatment, and research of neurological disorders.

Top employers
According to the city's 2019 Comprehensive Annual Financial Report, the top employers in the city proper are:

Fine arts

The Dayton Region ranked within the top 10% in the nation in arts and culture. In a 2012 readers' poll by American Style magazine, Dayton ranked #2 in the country among mid-size cities as an arts destination, ranking higher than larger cities such as Atlanta, St. Louis, and Cincinnati. Dayton is the home of the Dayton Art Institute.

The Benjamin and Marian Schuster Performing Arts Center in downtown Dayton is a world-class performing arts center and the home venue of the Dayton Philharmonic Orchestra, Dayton Opera, and the Dayton Ballet. In addition to philharmonic and opera performances, the Schuster Center hosts concerts, lectures, and traveling Broadway shows, and is a popular spot for weddings and other events. The historic Victoria Theatre in downtown Dayton hosts concerts, traveling Broadway shows, ballet, a summertime classic film series, and more. The Loft Theatre, also downtown, is the home of the Human Race Theatre Company. The Dayton Playhouse, in West Dayton, is the site of numerous plays and theatrical productions. Between 1957 and 1995, the Kenley Players presented live theater productions in Dayton. In 2013, John Kenley was inducted into the Dayton Theatre Hall of Fame. Dayton is also home to the Winter Guard International world finals, hosting finals for winter guard, indoor percussion, and indoor winds.

Dayton is the home to several ballet companies including:
 * The Dayton Ballet, one of the oldest professional dance companies in the United States. The Dayton Ballet runs the Dayton Ballet School, the oldest dance school in Dayton and one of the oldest in the country. It is the only ballet school in the Miami Valley associated with a professional dance company.
 * The Dayton Contemporary Dance Company (established in 1968), which hosts the largest repertory of African-American-based contemporary dance in the world. The company travels nationally and internationally and has been recognized by critics worldwide.

Front Street, the largest artists' collective in Dayton, is housed in three industrial buildings on East Second Street.

Entertainment

The Vectren Dayton Air Show is an annual air show that takes place at the Dayton International Airport. The Vectren Dayton Airshow is one of the largest air shows in the United States.

The Dayton area is served by Five Rivers MetroParks, encompassing 14161 acres over 23 facilities for year-round recreation, education, and conservation. In cooperation with the Miami Conservancy District, the MetroParks maintains over 70 mi of paved, multi-use scenic trails that connect Montgomery County with Greene, Miami, Warren, and Butler counties.

Dayton was home to a thriving funk music scene from the 1970s to the early 1980s, that included bands such as Ohio Players, Roger Troutman & Zapp, Lakeside, Sun, Dayton, Heatwave, and Slave.

Dayton was also the birthplace to several influential indie and punk bands such as The Breeders, Guided by Voices, and Brainiac.

From 1996 to 1998, Dayton hosted the National Folk Festival. Since then, the annual Cityfolk Festival has continued to bring folk, ethnic, and world music and arts to Dayton. The Five Rivers MetroParks also owns and operates the PNC Second Street Market near downtown Dayton.

The Dayton area hosts several arenas and venues. South of Dayton in Kettering is the Fraze Pavilion, whose notable performances have included the Backstreet Boys, Boston, and Steve Miller Band. South of downtown, on the banks of the Great Miami River, is the University of Dayton Arena, home venue for the University of Dayton Flyers basketball teams and the location of various other events and concerts. It also hosts the Winter Guard International championships, at which hundreds of percussion and color guard ensembles from around the world compete. In addition, the Dayton Amateur Radio Association hosts the annual Dayton Hamvention, North America's largest hamfest, at the Greene County Fairgrounds in nearby Xenia. The Nutter Center, which is just east of Dayton in the suburb of Fairborn, is the home arena for athletics of Wright State University and the former Dayton Bombers hockey team. This venue is used for many concerts, community events, and various national traveling shows and performances.

The Oregon District is a historic residential and commercial district in southeast downtown Dayton. The district is populated with art galleries, specialty shops, pubs, nightclubs, and coffee houses.

The city of Dayton is also host to yearly festivals, such as the Dayton Celtic Festival, the Dayton Blues Festival, Dayton Music Fest, Urban Nights, Women in Jazz, the African American and Cultural Festival, and the Dayton Reggae Fest.

Cuisine
The city's fine dining restaurants include The Pine Club, a nationally known steakhouse. Dayton is home to a variety of pizza chains that have become woven into local culture, the most notable of which are Cassano's and Marion's Piazza, both of which produce Dayton-style pizza, which has a thin, crisp, salty crust dusted on the bottom with cornmeal and topped with a thin layer of thick unsweetened sauce. Cheese and other topping ingredients are heavily distributed and spread edge-to-edge with no outer rim of crust, and the finished pizza is cut into bite-size squares.

Notable Dayton-based restaurant chains include Hot Head Burritos.

In addition to restaurants, the city is also home to Esther Price Candies, a candy and chocolate company, and Mike-sells, the oldest potato chip company in the United States.

The city began developing a reputation for its number of breweries and craft beer venues by the late 2010s.

Religion
Many major religions are represented in Dayton. Christianity is represented in Dayton by dozens of denominations and their respective churches. Notable Dayton churches include the First Lutheran Church, Sacred Heart Church, and Ginghamsburg Church. Dayton's Muslim community is largely represented by the Islamic Society of Greater Dayton (ISGD), a Muslim community that includes a mosque on Josie Street. Dayton is also home to the United Theological Seminary, one of 13 seminaries affiliated with the United Methodist Church. Judaism is represented by Temple Israel. Hinduism is represented by the Hindu Temple of Dayton. Old North Dayton also has a number of Catholic churches built by immigrants from Lithuania, Poland, Hungary, and Germany.

Tourism
Tourism also accounts for one out of every 14 private sector jobs in the county. Tourism in the Dayton region is led by the National Museum of the United States Air Force at Wright-Patterson Air Force Base, the largest and oldest military aviation museum in the world. The museum draws over 1.3 million visitors per year and is one of the most-visited tourist attractions in Ohio. The museum houses the National Aviation Hall of Fame.

Other museums also play significant roles in the tourism and economy of the Dayton area. The Dayton Art Institute, a museum of fine arts, owns collections containing more than 20,000 objects spanning 5,000 years of art and archaeological history. The Dayton Art Institute was rated one of the top 10 best art museums in the United States for children. The Boonshoft Museum of Discovery is a children's museum of science with numerous exhibits, one of which includes an indoor zoo with nearly 100 different animals.

There are also some notable historical museums in the region. The Dayton Aviation Heritage National Historical Park, operated by the National Park Service, commemorates the lives and achievements of Dayton natives Orville and Wilbur Wright and Paul Laurence Dunbar. The Wright brothers' famous Wright Flyer III aircraft is housed in a museum at Carillon Historical Park. Dayton is also home to America's Packard Museum, which contains many restored historical Packard vehicles. SunWatch Indian Village/Archaeological Park, a partially reconstructed 12th-century prehistoric American Indian village, is on the south end of Dayton; it is organized around a central plaza dominated by wood posts forming an astronomical calendar. The park includes a museum where visitors can learn about the Indian history of the Miami Valley.

Parks and recreation
Dayton was named National Geographic's outdoor adventure capital of the Midwest in 2019 due in large part to the metropolitan area's revitalized Five Rivers MetroPark, extensive bicycle and jogging trail system, urban green spaces, lakes and camping areas.

In cooperation with the Miami Conservancy District, Five Rivers MetroParks hosts 340 miles of paved trails, the largest network of paved off-street trails in the United States. The regional trail system represents over 35% of the 900 miles in Ohio's off-street trail network. In 2010, the city of Troy was named "bike friendly" by the League of American Bicyclists, which gave the city the organization's bronze designation. The honorable mention made Dayton one of two cities in Ohio to receive the award, the other being Columbus, and one of 15 cities nationwide.

Sports
The Dayton area is home to several minor league and semi pro teams, as well as NCAA Division I sports programs.

The Dayton Dragons professional baseball team is a Class A minor league affiliate for the Cincinnati Reds. The Dayton Dragons are the first (and only) team in minor league baseball history to sell out an entire season before it began and was voted as one of the top 10 hottest tickets to get in all of professional sports by Sports Illustrated. The Dayton Dragons 815 consecutive sellouts surpassed the NBA's Portland Trail Blazers for the longest sellout streak across all professional sports in the U.S.

The University of Dayton and Wright State University both host NCAA basketball. The University of Dayton Arena has hosted more games in the NCAA men's basketball tournament over its history than any other venue. UD Arena is also the site of the First Round games of the NCAA Tournament. In 2012, eight teams competed for the final four spots in the NCAA basketball tournament. Wright State University's NCAA men's basketball is the Wright State Raiders and the University of Dayton's NCAA men's basketball team is the Dayton Flyers.

The Dayton Gems were a minor league ice hockey team in the International Hockey League from 1964 to 1977, 1979 to 1980, and most recently 2009 to 2012. The Dayton Bombers were an ECHL ice hockey team from 1991 to 2009. They most recently played the North Division of the ECHL's American Conference. In June 2009, it was announced the Bombers would turn in their membership back to the league.

Despite the folding of the Bombers, hockey remained in Dayton as the Dayton Gems of the International Hockey League were formed in the fall of 2009 at Hara Arena. The Gems folded after the 2011–12 season. Shortly after the Gems folded, it was announced a new team, the Dayton Demonz, would begin play in 2012 in the Federal Hockey League (FHL). The Demonz folded in 2015 and were immediately replaced by the Dayton Demolition, also in the FHL. However, the Demolition would cease operations after only one season when Hara Arena decided to close due to financial difficulties.

Dayton hosted the first American Professional Football Association game (precursor to the NFL). The game was played at Triangle Park between the Dayton Triangles and the Columbus Panhandles on October 3, 1920, and is considered one of the first professional football games ever played. Football teams in the Dayton area include the Dayton Flyers and the Dayton Sharks.

The Dayton region is also known for the many golf courses and clubs that it hosts. The Miami Valley Golf Club, Moraine Country Club, NCR Country Club, and the Pipestone Golf Course are some of the more notable courses. Also, several PGA Championships have been held at area golf courses. The Miami Valley Golf Club hosted the 1957 PGA Championship, the Moraine Country Club hosted the 1945 PGA Championship, and the NCR Country club hosted the 1969 PGA Championship. Additionally, NCR CC hosted the 1986 U.S. Women's Open, the 2005 U.S. Senior Open, the 2013 State Team Championships and most recently the 2022 Senior Women's Open. Other notable courses include the Yankee Trace Golf Club, the Beavercreek Golf Club, Dayton Meadowbrook Country Club, Sycamore Creek Country Club, Heatherwoode Golf Club, Community Golf Course, and Kitty Hawk Golf Course.

The city of Dayton is the home to the Dayton Area Rugby Club which hosts their home games at the Dayton Rugby Grounds. As of 2018, the club fields two men's and one women's side for Rugby Union and several Rugby Sevens sides. The club also hosts the annual Gem City 7's tournament.

Government
The Dayton City Commission is composed of the mayor and four city commissioners. Each city commission member is elected at-large on a non-partisan basis for four-year, overlapping terms. All policy items are decided by the city commission, which is empowered by the City Charter to pass ordinances and resolutions, adopt regulations, and appoint the city manager. The city manager is responsible for budgeting and implementing policies and initiatives. Dayton was the first large American city to adopt the city manager (Henry Matson Waite) form of municipal government, in 1913.

Public schools
Dayton Public Schools operates 34 schools that serve 16,855 students, including:
 * Belmont High
 * Meadowdale High
 * Paul Laurence Dunbar High
 * Ponitz Career Technology Center
 * Stivers School for the Arts
 * Thurgood Marshall High

Private schools
The city of Dayton has more than 35 private schools within the city, including:
 * Archbishop Alter High School
 * Carroll High School
 * Chaminade Julienne Catholic High School
 * Dayton Christian School
 * Dominion Academy of Dayton
 * The Miami Valley School
 * Spring Valley Academy

Charter schools
Dayton has 33 charter schools. Three of the top five charter schools named in 2011 are K–8 schools managed by National Heritage Academies. Notable charter schools include:
 * Dayton Early College Academy
 * Emerson Academy
 * North Dayton School of Discovery
 * Pathway School of Discovery
 * Richard Allen Schools

Colleges and universities
The Dayton area was ranked tenth for higher education among metropolitan areas in the United States by Forbes in 2009. The city is home to two major universities. The University of Dayton is a private, Catholic institution founded in 1850 by the Marianist order. It has the only American Bar Association (ABA)-approved law school in the Dayton area. The University of Dayton is Ohio's largest private university and is also home to the University of Dayton Research Institute, which ranks third in the nation for sponsored materials research, and the Center for Tissue Regeneration and Engineering at Dayton, which focuses on human tissue regeneration.

The public Wright State University became a state university in 1967. Wright State University established the National Center for Medical Readiness, a national training program for disaster preparedness and relief. Wright State's Boonshoft School of Medicine is the Dayton area's only medical school and is a leader in biomedical research.

Dayton is also home to Sinclair Community College, the largest community college at a single location in Ohio and one of the nation's largest community colleges. Sinclair is acclaimed as one of the country's best community colleges. Sinclair was founded as the YMCA college in 1887.

Other schools just outside Dayton that shape the educational landscape are Antioch College and Antioch University, both in Yellow Springs, Central State University in Wilberforce, Kettering College of Medical Arts and School of Advertising Art in Kettering, DeVry University in Beavercreek, Cedarville University, Clark State Community College and Wittenberg University in Springfield. The Air Force Institute of Technology, which was founded in 1919 and serves as a graduate school for the United States Air Force, is at the nearby Wright-Patterson Air Force Base.

Institutions

 * Boonshoft School of Medicine
 * Dayton Art Institute
 * Ohio Institute of Photography and Technology
 * School of Advertising Art
 * Wright State University

Print
Dayton is served in print by The Dayton Daily News, the city's sole remaining daily newspaper. The Dayton Daily News is owned by Cox Enterprises. The Dayton region's main business newspaper is the Dayton Business Journal. The Dayton City Paper, a community paper focused on music, art, and independent thought ceased operation in 2018. The Dayton Weekly News has been published since 1993, providing news and information to Dayton's African-American community.

There are numerous magazines produced in and for the Dayton region. The Dayton Magazine provides insight into arts, food, and events. Focus on Business is published by the Chamber of Commerce to provide awareness of companies and initiatives affecting the regional economy

Television
Nielsen Media Research ranked the 11-county Dayton television market as the No. 62 market in the United States. The market is served by stations affiliated with major American networks including: WDTN, channel 2 – NBC, operated by Nexstar Media Group; WHIO-TV, channel 7 – CBS, operated by Cox Media Group; WPTD, channel 16 – PBS, operated by ThinkTV, which also operates WPTO, assigned to Oxford; WKEF, channel 22 – ABC/Fox, operated by Sinclair Broadcasting; WBDT, channel 26 – The CW, operated by Vaughan Media (a shell corporation of Nexstar), assigned to Springfield; WKOI-TV, channel 43 – Ion Television, assigned to Richmond, Indiana; and WRGT-TV, channel 45 – My Network TV, operated under a local marketing agreement by Sinclair Broadcasting. The nationally syndicated morning talk show The Daily Buzz originated from WBDT, the former ACME Communications property in Miamisburg, before moving to its current home in Florida.

Radio
Dayton is also served by 42 AM and FM radio stations directly, and numerous other stations are heard from elsewhere in southwest Ohio, which serve outlying suburbs and adjoining counties.

Public transit
The Greater Dayton Regional Transit Authority (RTA) operates public bus routes in the Dayton metro area. In addition to routes covered by traditional diesel-powered buses, RTA has several electric trolley bus routes. The Dayton trolleybus system is the second longest-running of the four remaining trolleybus systems in the U.S., having entered service in 1933. It is the present manifestation of an electric transit service that has operated continuously in Dayton since 1888.

Dayton operates a Greyhound Station which provides inter-city bus transportation to and from Dayton. The hub is in the Greater Dayton Regional Transit Authority North-West hub in Trotwood.

Airports

Dayton International Airport lies in a northern exclave of the city and offers service to 21 markets through 10 airlines. In 2008, it served 2.9 million passengers. The Dayton International Airport is also a significant regional air freight hub hosting FedEx Express, UPS Airlines, United States Postal Service, and major commercial freight carriers.

The Dayton area also has several regional airports. The Dayton–Wright Brothers Airport is a general aviation airport owned by the City of Dayton 10 mi south of the central business district of Dayton on Springboro Pike in Miami Township. It serves as the reliever airport for Dayton International Airport. The airport primarily serves corporate and personal aircraft users. The Dahio Trotwood Airport, also known as Dayton-New Lebanon Airport, is a privately owned, public-use airport 7 mi west of the central business district of Dayton. The Moraine Airpark is a privately owned, public-use airport 4 mi southwest of the city of Dayton.

Major highways
The Dayton region is primarily served by three interstates:
 * Interstate 75 runs north to south through the city of Dayton and many of Dayton's north and south suburbs, including Kettering and Centerville south of Dayton and Vandalia, Tipp City, and Troy north of Dayton.
 * Interstate 70 is a major east–west interstate that runs through many of Dayton's east and west suburbs, including Huber Heights, Butler Township, Englewood, and Brookville, and intersects with I-75 in Vandalia, Ohio, just north of the city. This intersection of I-70 and I-75 is also known as "Freedom Veterans Crossroads", which was officially named by the U.S. Department of Transportation in 2004. I-70 is the major route to the airport.
 * Interstate 675 is a partial interstate ring on the southeastern and eastern suburbs of Dayton. It runs northeast to south and connects to I-70 to the northeast and I-75 to the south.

Other major routes for the region include:
 * US 35 is a major limited access east–west highway that bisects the city. It is most widely used between Drexel and Xenia.
 * Route 40 is a major east–west highway that runs parallel to (and 2 miles north of) I-70
 * State Route 4 is a freeway that is most heavily traveled between I-75 and I-70.
 * State Route 444 is north–south state highway. Its southern terminus is at its interchange with Route 4, and its northern terminus is at Interstate 675. This limited-access road serves Dayton and Fairborn and is a significant route to access points serving Wright-Patterson Air Force Base.

From 2010 through 2017, the Ohio Department of Transportation (ODOT) performed a $533 million construction project to modify, reconstruct and widen I-75 through downtown Dayton, from Edwin C Moses Blvd. to Stanley Avenue.

Rail
Dayton hosts several inter-modal freight railroad terminals. Two Class I railroads, CSX and Norfolk Southern Railway, operate switching yards in the city.

Formerly the Baltimore and Ohio Railroad, New York Central Railroad and the Pennsylvania Railroad, and afterward, Amtrak made long-distance passenger train stops at Dayton Union Station on S. Sixth Street. The last train leaving there was the National Limited in October 1979.

Sister cities
Dayton's sister cities are:
 * Sarajevo, Bosnia and Herzegovina
 * Augsburg, Germany
 * Holon, Israel
 * Monrovia, Liberia
 * Ōiso, Japan
 * Rushmoor, England

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title: Dayton, Ohio


text:
Diode

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction and high (ideally infinite) resistance in the other.

A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. It has an exponential current–voltage characteristic. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other semiconducting materials such as gallium arsenide and germanium are also used.

The obsolete thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate.

Among many uses, diodes are found in rectifiers to convert alternating current (AC) power to direct current (DC), demodulation in radio receivers, and can even be used for logic or as temperature sensors. A common variant of a diode is a light-emitting diode, which is used as electric lighting and status indicators on electronic devices.

Unidirectional current flow
The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking it in the opposite direction (the reverse direction). Its hydraulic analogy is a check valve. This unidirectional behavior can convert alternating current (AC) to direct current (DC), a process called rectification. As rectifiers, diodes can be used for such tasks as extracting modulation from radio signals in radio receivers.

Threshold voltage
A diode's behavior is often simplified as having a forward threshold voltage or turn-on voltage or cut-in voltage, above which there is significant current and below which there is almost no current, which depends on a diode's composition: This voltage may loosely be referred to simply as the diode's forward voltage drop or just voltage drop, since a consequence of the steepness of the exponential is that a diode's voltage drop will not significantly exceed the threshold voltage under normal forward bias operating conditions. Datasheets typically quote a typical or maximum forward voltage (VF) for a specified current and temperature (e.g. 20 mA and 25 °C for LEDs), so the user has a guarantee about when a certain amount of current will kick in. At higher currents, the forward voltage drop of the diode increases. For instance, a drop of 1 V to 1.5 V is typical at full rated current for silicon power diodes. (See also: )

However, a semiconductor diode's exponential current–voltage characteristic is really more gradual than this simple on–off action. Although an exponential function may appear to have a definite "knee" around this threshold when viewed on a linear scale, the knee is an illusion that depends on the scale of y-axis representing current. In a semi-log plot (using a logarithmic scale for current and a linear scale for voltage), the diode's exponential curve instead appears more like a straight line.

Since a diode's forward-voltage drop varies only a little with the current, and is more so a function of temperature, this effect can be used as a temperature sensor or as a somewhat imprecise voltage reference.

Reverse breakdown
A diode's high resistance to current flowing in the reverse direction suddenly drops to a low resistance when the reverse voltage across the diode reaches a value called the breakdown voltage. This effect is used to regulate voltage (Zener diodes) or to protect circuits from high voltage surges (avalanche diodes).

Other functions
A semiconductor diode's current–voltage characteristic can be tailored by selecting the semiconductor materials and the doping impurities introduced into the materials during manufacture. These techniques are used to create special-purpose diodes that perform many different functions. For example, to electronically tune radio and TV receivers (varactor diodes), to generate radio-frequency oscillations (tunnel diodes, Gunn diodes, IMPATT diodes), and to produce light (light-emitting diodes). Tunnel, Gunn and IMPATT diodes exhibit negative resistance, which is useful in microwave and switching circuits.

Diodes, both vacuum and semiconductor, can be used as shot-noise generators.

History

Thermionic (vacuum-tube) diodes and solid-state (semiconductor) diodes were developed separately, at approximately the same time, in the early 1900s, as radio receiver detectors. Until the 1950s, vacuum diodes were used more frequently in radios because the early point-contact semiconductor diodes were less stable. In addition, most receiving sets had vacuum tubes for amplification that could easily have the thermionic diodes included in the tube (for example the 12SQ7 double diode triode), and vacuum-tube rectifiers and gas-filled rectifiers were capable of handling some high-voltage/high-current rectification tasks better than the semiconductor diodes (such as selenium rectifiers) that were available at that time.

In 1873, Frederick Guthrie observed that a grounded, white-hot metal ball brought in close proximity to an electroscope would discharge a positively charged electroscope, but not a negatively charged electroscope. In 1880, Thomas Edison observed unidirectional current between heated and unheated elements in a bulb, later called Edison effect, and was granted a patent on application of the phenomenon for use in a DC voltmeter. About 20 years later, John Ambrose Fleming (scientific adviser to the Marconi Company and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on 16 November 1904 (followed by in November 1905). Throughout the vacuum tube era, valve diodes were used in almost all electronics such as radios, televisions, sound systems, and instrumentation. They slowly lost market share beginning in the late 1940s due to selenium rectifier technology and then to semiconductor diodes during the 1960s. Today they are still used in a few high power applications where their ability to withstand transient voltages and their robustness gives them an advantage over semiconductor devices, and in musical instrument and audiophile applications.

In 1874, German scientist Karl Ferdinand Braun discovered the "unilateral conduction" across a contact between a metal and a mineral. Indian scientist Jagadish Chandra Bose was the first to use a crystal for detecting radio waves in 1894. The crystal detector was developed into a practical device for wireless telegraphy by Greenleaf Whittier Pickard, who invented a silicon crystal detector in 1903 and received a patent for it on 20 November 1906. Other experimenters tried a variety of other minerals as detectors. Semiconductor principles were unknown to the developers of these early rectifiers. During the 1930s understanding of physics advanced and in the mid-1930s researchers at Bell Telephone Laboratories recognized the potential of the crystal detector for application in microwave technology. Researchers at Bell Labs, Western Electric, MIT, Purdue and in the UK intensively developed point-contact diodes (crystal rectifiers or crystal diodes) during World War II for application in radar. After World War II, AT&T used these in its microwave towers that criss-crossed the United States, and many radar sets use them even in the 21st century. In 1946, Sylvania began offering the 1N34 crystal diode. During the early 1950s, junction diodes were developed.

In 2022, the first superconducting diode effect without an external magnetic field was realized.

Etymology
At the time of their invention, asymmetrical conduction devices were known as rectifiers. In 1919, the year tetrodes were invented, William Henry Eccles coined the term diode from the Greek roots di (from δί), meaning 'two', and ode (from οδός), meaning 'path'. The word diode however was already in use, as were triode, tetrode, pentode, hexode, as terms of multiplex telegraphy.

Although all diodes rectify, "rectifier" usually applies to diodes used for power supply, to differentiate them from diodes intended for small signal circuits.

Vacuum tube diodes
A thermionic diode is a thermionic-valve device consisting of a sealed, evacuated glass or metal envelope containing two electrodes: a cathode and a plate. The cathode is either indirectly heated or directly heated. If indirect heating is employed, a heater is included in the envelope.

In operation, the cathode is heated to red heat, around 800–1000 C. A directly heated cathode is made of tungsten wire and is heated by a current passed through it from an external voltage source. An indirectly heated cathode is heated by infrared radiation from a nearby heater that is formed of Nichrome wire and supplied with current provided by an external voltage source.

The operating temperature of the cathode causes it to release electrons into the vacuum, a process called thermionic emission. The cathode is coated with oxides of alkaline earth metals, such as barium and strontium oxides. These have a low work function, meaning that they more readily emit electrons than would the uncoated cathode.

The plate, not being heated, does not emit electrons; but is able to absorb them.

The alternating voltage to be rectified is applied between the cathode and the plate. When the plate voltage is positive with respect to the cathode, the plate electrostatically attracts the electrons from the cathode, so a current of electrons flows through the tube from cathode to plate. When the plate voltage is negative with respect to the cathode, no electrons are emitted by the plate, so no current can pass from the plate to the cathode.

Point-contact diodes
Point-contact diodes were developed starting in the 1930s, out of the early crystal detector technology, and are now generally used in the 3 to 30 gigahertz range. Point-contact diodes use a small diameter metal wire in contact with a semiconductor crystal, and are of either non-welded contact type or welded contact type. Non-welded contact construction utilizes the Schottky barrier principle. The metal side is the pointed end of a small diameter wire that is in contact with the semiconductor crystal. In the welded contact type, a small P region is formed in the otherwise N-type crystal around the metal point during manufacture by momentarily passing a relatively large current through the device. Point contact diodes generally exhibit lower capacitance, higher forward resistance and greater reverse leakage than junction diodes.

p–n junction diode
A p–n junction diode is made of a crystal of semiconductor, usually silicon, but germanium and gallium arsenide are also used. Impurities are added to it to create a region on one side that contains negative charge carriers (electrons), called an n-type semiconductor, and a region on the other side that contains positive charge carriers (holes), called a p-type semiconductor. When the n-type and p-type materials are attached together, a momentary flow of electrons occurs from the n to the p side resulting in a third region between the two where no charge carriers are present. This region is called the depletion region because there are no charge carriers (neither electrons nor holes) in it. The diode's terminals are attached to the n-type and p-type regions. The boundary between these two regions, called a p–n junction, is where the action of the diode takes place. When a sufficiently higher electrical potential is applied to the P side (the anode) than to the N side (the cathode), it allows electrons to flow through the depletion region from the N-type side to the P-type side. The junction does not allow the flow of electrons in the opposite direction when the potential is applied in reverse, creating, in a sense, an electrical check valve.

Schottky diode
Another type of junction diode, the Schottky diode, is formed from a metal–semiconductor junction rather than a p–n junction, which reduces capacitance and increases switching speed.

Current–voltage characteristic
A semiconductor diode's behavior in a circuit is given by its current–voltage characteristic. The shape of the curve is determined by the transport of charge carriers through the so-called depletion layer or depletion region that exists at the p–n junction between differing semiconductors. When a p–n junction is first created, conduction-band (mobile) electrons from the N-doped region diffuse into the P-doped region where there is a large population of holes (vacant places for electrons) with which the electrons "recombine". When a mobile electron recombines with a hole, both hole and electron vanish, leaving behind an immobile positively charged donor (dopant) on the N side and negatively charged acceptor (dopant) on the P side. The region around the p–n junction becomes depleted of charge carriers and thus behaves as an insulator.

However, the width of the depletion region (called the depletion width) cannot grow without limit. For each electron–hole pair recombination made, a positively charged dopant ion is left behind in the N-doped region, and a negatively charged dopant ion is created in the P-doped region. As recombination proceeds and more ions are created, an increasing electric field develops through the depletion zone that acts to slow and then finally stop recombination. At this point, there is a "built-in" potential across the depletion zone.

Reverse bias
If an external voltage is placed across the diode with the same polarity as the built-in potential, the depletion zone continues to act as an insulator, preventing any significant electric current flow (unless electron–hole pairs are actively being created in the junction by, for instance, light; see photodiode).

Forward bias
However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed, resulting in a substantial electric current through the p–n junction (i.e. substantial numbers of electrons and holes recombine at the junction) that increases exponentially with voltage.

Operating regions

A diode's current–voltage characteristic can be approximated by four operating regions. From lower to higher bias voltages, these are:

 * Breakdown: At very large reverse bias, beyond the peak inverse voltage (PIV), a process called reverse breakdown occurs that causes a large increase in current (i.e., a large number of electrons and holes are created at, and move away from the p–n junction) that usually damages the device permanently. The avalanche diode is deliberately designed for use in that manner. In the Zener diode, the concept of PIV is not applicable. A Zener diode contains a heavily doped p–n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material, such that the reverse voltage is "clamped" to a known value (called the Zener voltage), and avalanche does not occur. Both devices, however, do have a limit to the maximum current and power they can withstand in the clamped reverse-voltage region. Also, following the end of forwarding conduction in any diode, there is reverse current for a short time. The device does not attain its full blocking capability until the reverse current ceases.
 * Reverse biased: For a bias between breakdown and 0 V, the reverse current is very small and asymptotically approaches -Is. For a normal P–N rectifier diode, the reverse current through the device is in the micro-ampere (μA) range. However, this is temperature dependent, and at sufficiently high temperatures, a substantial amount of reverse current can be observed (mA or more). There is also a tiny surface leakage current caused by electrons simply going around the diode as though it were an imperfect insulator.DiodeGenCharacteristics1.jpg I–V (logarithmic current vs. linear voltage) graph of various diodes.]]
 * Forward biased: The current–voltage curve is exponential, approximating the Shockley diode equation. When plotted using a linear current scale, a smooth "knee" appears, but no clear threshold voltage is visible on a semi-log graph.

 * Leveling off: At larger forward currents the current–voltage curve starts to be dominated by the ohmic resistance of the bulk semiconductor. The curve is no longer exponential, it is asymptotic to a straight line whose slope is the bulk resistance. This region is particularly important for power diodes and can be modeled by a Shockley ideal diode in series with a fixed resistor.

Shockley diode equation
The Shockley ideal diode equation or the diode law (named after the bipolar junction transistor co-inventor William Bradford Shockley) models the exponential current–voltage (I–V) relationship of diodes in moderate forward or reverse bias. The article Shockley diode equation provides details.

Small-signal behavior
At forward voltages less than the saturation voltage, the voltage versus current characteristic curve of most diodes is not a straight line. The current can be approximated by $$I = I_\text{S} e^{V_\text{D}/(n V_\text{T})}$$ as explained in the Shockley diode equation article.

In detector and mixer applications, the current can be estimated by a Taylor's series. The odd terms can be omitted because they produce frequency components that are outside the pass band of the mixer or detector. Even terms beyond the second derivative usually need not be included because they are small compared to the second order term. The desired current component is approximately proportional to the square of the input voltage, so the response is called square law in this region.

Reverse-recovery effect
Following the end of forwarding conduction in a p–n type diode, a reverse current can flow for a short time. The device does not attain its blocking capability until the mobile charge in the junction is depleted.

The effect can be significant when switching large currents very quickly. A certain amount of "reverse recovery time" $t$r (on the order of tens of nanoseconds to a few microseconds) may be required to remove the reverse recovery charge $Q$r from the diode. During this recovery time, the diode can actually conduct in the reverse direction. This might give rise to a large current in the reverse direction for a short time while the diode is reverse biased. The magnitude of such a reverse current is determined by the operating circuit (i.e., the series resistance) and the diode is said to be in the storage-phase. In certain real-world cases it is important to consider the losses that are incurred by this non-ideal diode effect. However, when the slew rate of the current is not so severe (e.g. Line frequency) the effect can be safely ignored. For most applications, the effect is also negligible for Schottky diodes.

The reverse current ceases abruptly when the stored charge is depleted; this abrupt stop is exploited in step recovery diodes for the generation of extremely short pulses.

Types of semiconductor diode
Normal (p–n) diodes, which operate as described above, are usually made of doped silicon or germanium. Before the development of silicon power rectifier diodes, cuprous oxide and later selenium was used. Their low efficiency required a much higher forward voltage to be applied (typically 1.4 to 1.7 V per "cell", with multiple cells stacked so as to increase the peak inverse voltage rating for application in high voltage rectifiers), and required a large heat sink (often an extension of the diode's metal substrate), much larger than the later silicon diode of the same current ratings would require. The vast majority of all diodes are the p–n diodes found in CMOS integrated circuits, which include two diodes per pin and many other internal diodes.

 * Avalanche diodes
 * These are diodes that conduct in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. These are electrically very similar to Zener diodes (and are often mistakenly called Zener diodes), but break down by a different mechanism: the avalanche effect. This occurs when the reverse electric field applied across the p–n junction causes a wave of ionization, reminiscent of an avalanche, leading to a large current. Avalanche diodes are designed to break down at a well-defined reverse voltage without being destroyed. The difference between the avalanche diode (which has a reverse breakdown above about 6.2 V) and the Zener is that the channel length of the former exceeds the mean free path of the electrons, resulting in many collisions between them on the way through the channel. The only practical difference between the two types is they have temperature coefficients of opposite polarities.

 * Constant-current diodes
 * These are actually JFETs with the gate shorted to the source, and function like a two-terminal current-limiting analog to the voltage-limiting Zener diode. They allow a current through them to rise to a certain value, and then level off at a specific value. Also called CLDs, constant-current diodes, diode-connected transistors, or current-regulating diodes.

 * Crystal rectifiers or crystal diodes
 * These are point-contact diodes. The 1N21 series and others are used in mixer and detector applications in radar and microwave receivers.  The 1N34A is another example of a crystal diode.

 * Gunn diodes
 * These are similar to tunnel diodes in that they are made of materials such as GaAs or InP that exhibit a region of negative differential resistance. With appropriate biasing, dipole domains form and travel across the diode, allowing high frequency microwave oscillators to be built.

 * Light-emitting diodes (LEDs)
 * In a diode formed from a direct band-gap semiconductor, such as gallium arsenide, charge carriers that cross the junction emit photons when they recombine with the majority carrier on the other side. Depending on the material, wavelengths (or colors) from the infrared to the near ultraviolet may be produced. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time. All LEDs produce incoherent, narrow-spectrum light; "white" LEDs are actually a blue LED with a yellow scintillator coating, or combinations of three LEDs of a different color. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an opto-isolator.

 * Laser diodes
 * When an LED-like structure is contained in a resonant cavity formed by polishing the parallel end faces, a laser can be formed. Laser diodes are commonly used in optical storage devices and for high speed optical communication.

 * Thermal diodes
 * This term is used both for conventional p–n diodes used to monitor temperature because of their varying forward voltage with temperature, and for Peltier heat pumps for thermoelectric heating and cooling. Peltier heat pumps may be made from semiconductors, though they do not have any rectifying junctions, they use the differing behavior of charge carriers in N and P-type semiconductor to move heat.

 * Photodiodes
 * All semiconductors are subject to optical charge carrier generation. This is typically an undesired effect, so most semiconductors are packaged in light-blocking material. Photodiodes are intended to sense light (photodetector), so they are packaged in materials that allow light to pass, and are usually PIN (the kind of diode most sensitive to light). A photodiode can be used in solar cells, in photometry, or in optical communications. Multiple photodiodes may be packaged in a single device, either as a linear array or as a two-dimensional array. These arrays should not be confused with charge-coupled devices.

 * PIN diodes
 * A PIN diode has a central un-doped, or intrinsic, layer, forming a p-type/intrinsic/n-type structure. They are used as radio frequency switches and attenuators. They are also used as large-volume, ionizing-radiation detectors and as photodetectors. PIN diodes are also used in power electronics, as their central layer can withstand high voltages. Furthermore, the PIN structure can be found in many power semiconductor devices, such as IGBTs, power MOSFETs, and thyristors.

 * Schottky diodes
 * Schottky diodes are constructed from metal to semiconductor contact. They have a lower forward voltage drop than p–n junction diodes. Their forward voltage drop at forward currents of about 1 mA is in the range 0.15 V to 0.45 V, which makes them useful in voltage clamping applications and prevention of transistor saturation. They can also be used as low loss rectifiers, although their reverse leakage current is in general higher than that of other diodes. Schottky diodes are majority carrier devices and so do not suffer from minority carrier storage problems that slow down many other diodes—so they have a faster reverse recovery than p–n junction diodes. They also tend to have much lower junction capacitance than p–n diodes, which provides for high switching speeds and their use in high-speed circuitry and RF devices such as switched-mode power supply, mixers, and detectors.

 * Super barrier diodes
 * Super barrier diodes are rectifier diodes that incorporate the low forward voltage drop of the Schottky diode with the surge-handling capability and low reverse leakage current of a normal p–n junction diode.

 * Gold-doped diodes
 * As a dopant, gold (or platinum) acts as recombination centers, which helps the fast recombination of minority carriers. This allows the diode to operate at signal frequencies, at the expense of a higher forward voltage drop. Gold-doped diodes are faster than other p–n diodes (but not as fast as Schottky diodes). They also have less reverse-current leakage than Schottky diodes (but not as good as other p–n diodes). A typical example is the 1N914.

 * Snap-off or step recovery diodes
 * The term step recovery relates to the form of the reverse recovery characteristic of these devices. After a forward current has been passing in an SRD and the current is interrupted or reversed, the reverse conduction will cease very abruptly (as in a step waveform). SRDs can, therefore, provide very fast voltage transitions by the very sudden disappearance of the charge carriers.

 * Stabistors or forward reference diodes
 * The term stabistor refers to a special type of diodes featuring extremely stable forward voltage characteristics. These devices are specially designed for low-voltage stabilization applications requiring a guaranteed voltage over a wide current range and highly stable over temperature.

 * Transient voltage suppression diode (TVS)
 * These are avalanche diodes designed specifically to protect other semiconductor devices from high-voltage transients. Their p–n junctions have a much larger cross-sectional area than those of a normal diode, allowing them to conduct large currents to ground without sustaining damage.

 * Tunnel diodes or Esaki diodes
 * These have a region of operation showing negative resistance caused by quantum tunneling, allowing amplification of signals and very simple bistable circuits. Because of the high carrier concentration, tunnel diodes are very fast, may be used at low (mK) temperatures, high magnetic fields, and in high radiation environments. Because of these properties, they are often used in spacecraft.

 * Varicap or varactor diodes
 * These are used as voltage-controlled capacitors. These are important in PLL (phase-locked loop) and FLL (frequency-locked loop) circuits, allowing tuning circuits, such as those in television receivers, to lock quickly on to the frequency. They also enabled tunable oscillators in the early discrete tuning of radios, where a cheap and stable, but fixed-frequency, crystal oscillator provided the reference frequency for a voltage-controlled oscillator.

 * Zener diodes
 * These can be made to conduct in reverse bias (backward), and are correctly termed reverse breakdown diodes. This effect called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. The term Zener diodes is colloquially applied to several types of breakdown diodes, but strictly speaking, Zener diodes have a breakdown voltage of below 5 volts, whilst avalanche diodes are used for breakdown voltages above that value. In practical voltage reference circuits, Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient response of the diodes to near-zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes (see above). Two (equivalent) Zeners in series and in reverse order, in the same package, constitute a transient absorber (or Transorb, a registered trademark).

Graphic symbols
The symbol used to represent a particular type of diode in a circuit diagram conveys the general electrical function to the reader. There are alternative symbols for some types of diodes, though the differences are minor. The triangle in the symbols points to the forward direction, i.e. in the direction of conventional current flow.

Numbering and coding schemes
There are a number of common, standard and manufacturer-driven numbering and coding schemes for diodes; the two most common being the EIA/JEDEC standard and the European Pro Electron standard:

EIA/JEDEC
The standardized 1N-series numbering EIA370 system was introduced in the US by EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Most diodes have a 1-prefix designation (e.g., 1N4003). Among the most popular in this series were: 1N34A/1N270 (germanium signal), 1N914/1N4148 (silicon signal), 1N400x (silicon 1A power rectifier), and 1N580x (silicon 3A power rectifier).

JIS
The JIS semiconductor designation system has all semiconductor diode designations starting with "1S".

Pro Electron
The European Pro Electron coding system for active components was introduced in 1966 and comprises two letters followed by the part code. The first letter represents the semiconductor material used for the component (A = germanium and B = silicon) and the second letter represents the general function of the part (for diodes, A = low-power/signal, B = variable capacitance, X = multiplier, Y = rectifier and Z = voltage reference); for example:
 * AA-series germanium low-power/signal diodes (e.g., AA119)
 * BA-series silicon low-power/signal diodes (e.g., BAT18 silicon RF switching diode)
 * BY-series silicon rectifier diodes (e.g., BY127 1250V, 1A rectifier diode)
 * BZ-series silicon Zener diodes (e.g., BZY88C4V7 4.7V Zener diode)

Other common numbering/coding systems (generally manufacturer-driven) include:
 * GD-series germanium diodes (e.g., GD9) – this is a very old coding system
 * OA-series germanium diodes (e.g., OA47) – a coding sequence developed by Mullard, a UK company

Related devices
In optics, an equivalent device for the diode but with laser light would be the optical isolator, also known as an optical diode, that allows light to only pass in one direction. It uses a Faraday rotator as the main component.
 * Rectifier
 * Transistor
 * Thyristor or silicon controlled rectifier (SCR)
 * TRIAC
 * DIAC
 * Varistor

Radio demodulation
The first use for the diode was the demodulation of amplitude modulated (AM) radio broadcasts. The history of this discovery is treated in depth in the crystal detector article. In summary, an AM signal consists of alternating positive and negative peaks of a radio carrier wave, whose amplitude or envelope is proportional to the original audio signal. The diode rectifies the AM radio frequency signal, leaving only the positive peaks of the carrier wave. The audio is then extracted from the rectified carrier wave using a simple filter and fed into an audio amplifier or transducer, which generates sound waves via audio speaker.

In microwave and millimeter wave technology, beginning in the 1930s, researchers improved and miniaturized the crystal detector. Point contact diodes (crystal diodes) and Schottky diodes are used in radar, microwave and millimeter wave detectors.

Power conversion

Rectifiers are constructed from diodes, where they are used to convert alternating current (AC) electricity into direct current (DC). Automotive alternators are a common example, where the diode, which rectifies the AC into DC, provides better performance than the commutator or earlier, dynamo. Similarly, diodes are also used in Cockcroft–Walton voltage multipliers to convert AC into higher DC voltages.

Reverse-voltage protection
Since most electronic circuits can be damaged when the polarity of their power supply inputs are reversed, a series diode is sometimes used to protect against such situations. This concept is known by multiple naming variations that mean the same thing: reverse voltage protection, reverse polarity protection, and reverse battery protection.

Over-voltage protection
Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices. They are usually reverse-biased (non-conducting) under normal circumstances. When the voltage rises above the normal range, the diodes become forward-biased (conducting). For example, diodes are used in (stepper motor and H-bridge) motor controller and relay circuits to de-energize coils rapidly without the damaging voltage spikes that would otherwise occur. (A diode used in such an application is called a flyback diode). Many integrated circuits also incorporate diodes on the connection pins to prevent external voltages from damaging their sensitive transistors. Specialized diodes are used to protect from over-voltages at higher power (see Diode types above).

Logic gates
Diode-resistor logic constructs AND and OR logic gates. Functional completeness can be achieved by adding an active device to provide inversion (as done with diode-transistor logic).

Ionizing radiation detectors
In addition to light, mentioned above, semiconductor diodes are sensitive to more energetic radiation. In electronics, cosmic rays and other sources of ionizing radiation cause noise pulses and single and multiple bit errors. This effect is sometimes exploited by particle detectors to detect radiation. A single particle of radiation, with thousands or millions of electron volt, s of energy, generates many charge carrier pairs, as its energy is deposited in the semiconductor material. If the depletion layer is large enough to catch the whole shower or to stop a heavy particle, a fairly accurate measurement of the particle's energy can be made, simply by measuring the charge conducted and without the complexity of a magnetic spectrometer, etc. These semiconductor radiation detectors need efficient and uniform charge collection and low leakage current. They are often cooled by liquid nitrogen. For longer-range (about a centimeter) particles, they need a very large depletion depth and large area. For short-range particles, they need any contact or un-depleted semiconductor on at least one surface to be very thin. The back-bias voltages are near breakdown (around a thousand volts per centimeter). Germanium and silicon are common materials. Some of these detectors sense position as well as energy. They have a finite life, especially when detecting heavy particles, because of radiation damage. Silicon and germanium are quite different in their ability to convert gamma rays to electron showers.

Semiconductor detectors for high-energy particles are used in large numbers. Because of energy loss fluctuations, accurate measurement of the energy deposited is of less use.

Temperature measurements
A diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature, as in a silicon bandgap temperature sensor. From the Shockley ideal diode equation given above, it might appear that the voltage has a positive temperature coefficient (at a constant current), but usually the variation of the reverse saturation current term is more significant than the variation in the thermal voltage term. Most diodes therefore have a negative temperature coefficient, typically −2 mV/°C for silicon diodes. The temperature coefficient is approximately constant for temperatures above about 20 kelvin. Some graphs are given for 1N400x series, and CY7 cryogenic temperature sensor.

Current steering
Diodes will prevent currents in unintended directions. To supply power to an electrical circuit during a power failure, the circuit can draw current from a battery. An uninterruptible power supply may use diodes in this way to ensure that the current is only drawn from the battery when necessary. Likewise, small boats typically have two circuits each with their own battery/batteries: one used for engine starting; one used for domestics. Normally, both are charged from a single alternator, and a heavy-duty split-charge diode is used to prevent the higher-charge battery (typically the engine battery) from discharging through the lower-charge battery when the alternator is not running.

Diodes are also used in electronic musical keyboards. To reduce the amount of wiring needed in electronic musical keyboards, these instruments often use keyboard matrix circuits. The keyboard controller scans the rows and columns to determine which note the player has pressed. The problem with matrix circuits is that, when several notes are pressed at once, the current can flow backward through the circuit and trigger "phantom keys" that cause "ghost" notes to play. To avoid triggering unwanted notes, most keyboard matrix circuits have diodes soldered with the switch under each key of the musical keyboard. The same principle is also used for the switch matrix in solid-state pinball machines.

Waveform clipper
Diodes can be used to limit the positive or negative excursion of a signal to a prescribed voltage.

Clamper
A diode clamp circuit can take a periodic alternating current signal that oscillates between positive and negative values, and vertically displace it such that either the positive or the negative peaks occur at a prescribed level. The clamper does not restrict the peak-to-peak excursion of the signal, it moves the whole signal up or down so as to place the peaks at the reference level.

Computing exponentials & logarithms
The diode's exponential current–voltage relationship is exploited to evaluate exponentiation and its inverse function the logarithm using analog voltage signals (see ).

Abbreviations
Diodes are usually referred to as D for diode on PCBs. Sometimes the abbreviation CR for crystal rectifier is used.

title: Diode