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Dartmoor Preservation Association

'Fighting to keep Dartmoor wild and free since 1883.'
Dartmoor Preservation Association (DPA) is one of the oldest environmental or amenity bodies in the UK. It was founded in 1883. It concerns itself with Dartmoor, a National Park in Devon, south-west England. It began with two main areas of concern. Firstly, commoners' rights were being eroded through army use, including the firing of live artillery shells, and piecemeal enclosure of land around the margins. Secondly, there was increasing public interest in Dartmoor's scenery, archaeology, history and wildlife

The DPA has opposed what it considered to be unsuitable developments on Dartmoor throughout its history. In its founding year, the secretary, Robert Burnard persuaded the War Department not to fire on the Okehampton Firing Range on Saturdays to allow access to the public. Many battles have been fought since, particularly against the military presence and the proposed building of reservoirs on the moor, notably under the Chairmanship of Lady Sayer, granddaughter of Robert Burnard.

The DPA continues to follow the same objectives as when it was founded. For example, in June 2015, it supported the inhabitants of Widecombe-in-the-Moor against the erecting of a telecommunications mast in an area of pristine countryside against the wishes of the local population.

Dartmoor Preservation Association is a registered charity, Number 215665.

Background
Dartmoor is said to be one of the last remaining areas of wilderness in Britain, but it has been a managed landscape since the late Neolithic (3,000-2,500 BCE). The Bronze Age inhabitants (from 2,500 to 750 BCE) cleared ancient forest and developed farming. They made extensive use of surface moorstone in the construction of roundhouses (their remains now seen as "hut circles"), enclosures, land-dividing reaves, stone rows, stone circles, menhirs and kistvaens.

Farming has continued through the Medieval period to the present day, but a more disruptive activity to the landscape was the appearance of tin-mining, firstly by stream-working, then by lode-working and finally by underground mining. Many valleys have been dug over and scarred, leaving a rich industrial archaeology. Other activities such as newtake wall building, peat cutting, rabbit warrening, quarrying, clay extraction and the building of a prominent prison have all left marks on the moor. Recent undertakings have left more obvious changes: the building of reservoirs and the planting of conifer forests.

History of the association
The use of moorstone continued up to recent times with the extensive building of dry stone walls around farm newtakes. Later, stone was cut and dressed. The use of moorstone continued to such an extent that in 1847 boundary markers were cut around Pew Tor to protect it. Marker stones were erected around Roos Tor. The taking of stone started to change the Dartmoor landscape: for example Eric Hemery (writing in 1983) stated that Swell Tor had been "decapitated and disembowelled by the quarrymen".

In August 1881, a public meeting was convened by the Portreeve of Tavistock in the Guildhall to discuss the continued taking of stone, particularly from landmark tors. The DPA was founded in 1883. The protected area around Pew Tor was extended in December 1896. In 1901, the DPA commissioned a report into damage to ancient monuments, caused by the taking of stone for building and road-mending, and into unlawful enclosures of common land.

Commoners' rights
The first publication of the DPA, in 1890, was a short history of commoners' rights on Dartmoor and the commons of Devon. This notes a decrease in the numbers of animals even in medieval times: in 1296 – 5,000 cattle, 487 horses, 131 folds of sheep; in 1316 – 3,292 cattle, 368 horses, 100 folds of sheep. ''An important battle occurred in 1894 when the Corporation of London attempted to buy the whole of Dartmoor in order to pipe its water to Paddington alongside Brunel’s recently converted railway, when it went from broad gauge to standard gauge. The DPA led the revolt against this''. In 1897, the DPA went to court to fight successfully the enclosure of a section of Peter Tavy Great Common, in support of a farmer. Commoners rights seem to have been a settled issue in recent years: except for where they are impinged upon by the military presence.

Military use
Dartmoor Training Area has been used regularly for military training since 1873, although it was used earlier during the Napoleonic and Crimean Wars. In 1906–07, seven miles of roads were built on the north moor to facilitate the movement of guns. There are three established firing ranges at Okehampton, Willsworthy and Merrivale. The area taken up with live firing ranges is 9,187 ha and they are used on average 120 days each year. They are used for small arms, mortars and artillery smoke and illuminating shells.

The use of the moor by the military has been a major concern of the DPA since its founding. In its first year, Robert Burnard (DPA Secretary) persuaded the War Department not to fire on the Okehampton Firing Range on Saturdays so that there may be some public access to the area. Lady Sylvia Sayer was very outspoken about it being totally at odds with the area being designated as a National Park. In 1963 the DPA published a widely circulated 24-page booklet entitled Misuse of a National Park which includes photographs of unexploded shells lying on the open moor, corrugated iron buildings, large craters, a derelict tank used as a target, bullet marks on standing stones, etc. It also contains details of a 1958 incident in which a young boy was killed by a mortar shell near Cranmere Pool.

Since the 1960s there has been much less military damage and litter as a result of the DPA persuading the Services to be more cautious. The military have changed since the Victorian era, they now have 120 conservation groups across the Ministry of Defence (MOD), including Dartmoor Military Conservation Group. The current leases run for many years, with Cramber Tor most recently being granted a further 40-year licence.

Afforestation
Early afforestation occurred when Brimpts was planted with trees in 1862. The Forestry Commission was founded in 1919, following World War I and in that year the Duchy of Cornwall planted 800 acres of conifers at Fernworthy. In 1921, Plymouth Corporation planted conifers around Burrator Reservoir. The Forestry Commission planted Bellever and Laughter Tor farms in 1930-32 and in 1944-1945 Soussons Down was also planted. The DPA opposed these post-war plantings and R. Hansford Worth (1868-1950, a Plymouth engineer, scientist and antiquarian) delivered a lecture fiercely critical of the Duchy of Cornwall as the landowners at The Plymouth Athenaeum, using the argument of encroachment on the rights of common and loss of ancient monuments. DPA opposition to forestry on Dartmoor arose again in 1953 when it wrote a policy on woodlands in the then-new national park. Opposition was exercised when Hawn, Dendles and High House Wastes, all near Cornwood, were designated for tree planting in 1959. Argument continued while Hawns and Dendles Wastes were ploughed in 1960. High House Waste was purchased by the DPA in 1964 and the Nature Conservancy (UK) bought neighbouring Dendles in 1965. The situation in 2015 is that some of the Dartmoor plantations have been affected by the fungal disease Phytophthora ramorum which results in widespread clear felling to prevent further spread of the disease. The policy now is to replant with more native hardwood trees although more resistant conifers are also being used.

Reservoirs
There are eight Dartmoor reservoirs, with the earliest being Tottiford Reservoir, 1861. Three were built in the mid-20th century: Fernworthy, 1942; Avon, 1957 and Meldon, 1972, and the DPA fought many battles over these. It opposed plans for reservoirs on Brent Moor (1899) and Holne Moor (1901) where, later, the Avon Reservoir and Venford Reservoirs were respectively built. The DPA's opposition was supported in the House of Commons with argument made regarding the effects on the local water table. The DPA was one of many local and national amenity bodies that fought the building of the Meldon dam. The preservation battle for the Meldon valley was recorded in a DPA publication. The DPA offered a viable alternative site, Gorhuish Valley, for various reasons, including the fact that minerals such as arsenic would leach into the water supply if Meldon were selected. The Meldon story was discussed many times in Parliament. Another battle was fought against the flooding of the Swincombe valley to form another reservoir. This was rejected in parliament in 1970, revived in 1974 and finally resolved by the building of the Roadford Reservoir to the west of the moor. In 1985 the DPA used funds from a bequest to purchase 50 acres of land where the dam of a reservoir at Swincombe would have to be.

National Park designation
The National Parks and Access to the Countryside Act 1949 led to Dartmoor being one of the first four parks to be designated, by an order made on 15 August 1951 and confirmed on 30 October 1951. Shortly after this, the DPA tried to ensure that the new National Park was run by an independent committee and not by the Dartmoor Standing Committee that was a subcommittee of Devon County Council Planning Committee. The committee was reformed as Dartmoor National Park Committee under the Local Government Act 1972 but it was still a subcommittee of Devon County Council and as such it was not seen to be an independent guardian of the moor by the DPA. It was not until 1997 that an independent Dartmoor National Park Authority was enabled under the Environment Act 1995 as a free-standing local authority, forty-four years after the park was created, although it is still dominated by local authorities and government appointees.

North Hessary Tor TV mast
The DPA learned in October 1951 that the BBC planned to build a 750-foot television mast on North Hessary Tor, near Princetown, that was erected in 1955. This was to be a relay from a transmitting station at Wenvoe, South Wales. The DPA objected to this threat and sought expert opinion, offered alternative solutions, pressed for a public enquiry, engaged a lawyer, held public meetings, distributed pamphlets, wrote to the press and petitioned parliament. Eventually, a public enquiry was announced. When the decision was made to permit the mast, there were a number of conditions, included among them was that the development was built near the tor, leaving it still intact, and that its new approach road should not be fenced. During the process of obtaining land for the transmitter, one MP asked in the House of Commons: "Will the Assistant Postmaster-General bear in mind that we have no desire to hinder the provision of this station but that it is felt that ancient common rights such as these, that have existed for a thousand years, should be adequately protected or properly extinguished by due process of law?"

Sharpitor
During World War II, the Royal Air Force (RAF) built a mast and buildings on Peek Hill, as RAF Sharpitor. In 1956, permission was granted to rebuild the station as part of the "Gee" radio navigation system, to be occupied for ten years. There followed delay in leaving and a proposal was made in 1970 by Devon & Cornwall Police to use the mast, which was rejected. Then later that year Plymouth Corporation wanted to use the exposed site for housing juvenile offenders. This was also rejected, but Plymouth appealed. At a public enquiry in June 1973 Lady Sylvia Sayer represented the DPA and permission for development on the site was refused. A few years later, DPA fought successfully in support of South West Water (SWW) against renewed calls for a new reservoir at Swincombe. To mark the victory, Sylvia Sayer asked SWW if DPA could purchase the rocky outcrop of Sharpitor. The DPA purchased 32 acres in February 1984.

Okehampton bypass
Okehampton lies on the A30 main road, the shortest route from London to west Devon and Cornwall. The need for a bypass was mooted in 1963. In 1975, three routes were considered: a northern route through mainly farmland, a central route using a railway, and a southern route through Dartmoor National Park. In August 1976, the Department of the Environment announced the preferred route was through the National Park. A major event on the timeline of this project was a 96-day public enquiry from 1 May 1979 to 4 February 1980 held in Okehampton. In March 1984, the DPA with other organisations petitioned Parliament opposing compulsory purchase orders on public open spaces. The Secretary of State announced in July 1985 that he was introducing a bill to reverse the decision of a Joint Parliamentary Committee and confirm a route through the National Park. This was followed by a confirmation bill in November 1985 that was passed in the House of Lords on 5 December 1985. Construction started in November 1986 and the road was opened on 19 July 1988.

Since 2000
The DPA continues to follow the same objectives as when it was founded. The activities have widened, involving local partners, it has a calendar of events, walks and work days with its Conservation Team undertaking a variety of moorland projects, it funds the supply of walking boots to some children who need them for the Duke of Edinburgh Award Scheme through the Moor Boots Scheme, it collaborates with the Campaign for National Parks, it monitors the activities of Dartmoor National Park Authority who run the National Park. It objected to eight planning proposals (with success in seven cases), with many other achievements in the DPA Director's Annual Report. The DPA remains true to its original objectives and has also added other activities in support of Dartmoor and its inhabitants.

China clay expansion
The china clay industry on Dartmoor was established long before the DPA was founded. The earliest record of a china clay pit refers to Hook Lake in 1502. The area was surveyed around 1827 by Cornishmen with thirty years experience in the clay industry. They obtained a 21-year lease in 1830, from the Earl of Morley who owned the land, to work the area between Lee Moor and Shaugh Moor. A rival pit was opened at Leftlake in about 1850 and at Hemerdon and Broomage in about 1855. Further pits were opened at Cholwichtown, Whitehill Yeo and Wigford Down/Brisworthy (circa 1860). Others followed at Smallhanger and Headon in the 1870s. Redlake started working in 1910. China clay pits are open cast mines that result in large holes in the ground accompanied by large waste tips. Over time, the pits become larger and more ground is needed for the waste, changing the landscape: the effect of this can be seen from space.

The DPA argues that this is an activity that does not agree with the ethos of a National Park, whose purpose is to protect landscape from unsuitable development. In 1994, the National Park boundaries were changed to include common land at Shaugh Moor and exclude china clay worked land at Lee Moor. The DPA revived its campaign with the publication of a booklet in 1999 when the Blackabrook Valley, Crownhill Down and Shaugh Moor, near the popular tourist area of Cadover Bridge, all came under threat from exploitation or dumping of waste. The china clay companies relinquished planning permissions in 2001. However, in November 2009, the clay companies, Sibelco and Imerys, produced a report reviewing old mineral permissions under the Environment Act 1995 with a view to joining up two pits. A presumed Bronze Age barrow, known as Emmets Post, was to be removed and three other monuments may be affected. The DPA were recorded twice, with other bodies, in a Devon County Council Development Management Committee Report for their representations in securing the future of the three areas where planning permissions were relinquished in 2001. Oxford Archaeology held an open day during their excavation of Emmets Post in 2014 prior to its removal.

House of Lords reception
The DPA and Exmoor Society held a joint reception at the House of Lords on 6 November 2008, hosted by Baroness Mallalieu, to lobby members of both Houses of Parliament and relevant Ministers about ensuring that environmental schemes for the uplands are "fit for purpose". Both organisations funded an invited number of upland hill farmers to attend.

Whitehorse Hill excavation
The excavation in August 2011 on the north moor of a Bronze Age burial kistvaen, or cist, that was originally uncovered in 2001 was part-funded by the DPA, along with other bodies.

South West Uplands Federation Conference
A conference for the upland farmers of Bodmin Moor, Exmoor and Dartmoor was held as a joint venture between the South West Uplands Federation and the DPA. It was run by the DPA at Exeter Racecourse in October 2012, with 150 delegates. Speakers came from the Foundation for Common Land, the Forest of Dartmoor Commoners, the University of Gloucestershire, the National Farmers Union of England and Wales and the Open Spaces Society. The CEO raised sponsorship from Dartmoor National Park, Exmoor National Park, Natural England, Duchy of Cornwall and the Exmoor Society - this reflecting the standing of the DPA with those bodies.

Undergrounding power cables
Two major projects to underground overhead power cables in Dartmoor National Park have been completed in a joint project between Western Power Distribution, the South West Protected Landscapes Forum (SWPLF) and Dartmoor National Park Authority. The two schemes on Holne Moor and Walkhampton Common between them remove nearly 6 km of overhead line from open moorland. At nearly 5 km, the Walkhampton scheme is the largest to be undertaken in the South West region by Western Power Distribution. The old overhead line was readily visible from the B3212 Princetown to Yelverton Road, strung across Walkhampton Common from Devil's Elbow to just above Horseyeatt at Peek Hill. The works to provide the new underground supply were mainly undertaken on the highway to minimise the impact on the sensitive moorland landscape, its archaeology, wildlife and livestock. The DPA has supported the undergrounding of these visually intrusive power lines for many years.

The Dartmoor Conservation Garden
The Dartmoor Conservation Garden is a joint project between DPA and Dartmoor National Park Authority (DNPA) and is located in the Jack Wigmore Garden behind the High Moorland Centre in Princetown: this is a memorial garden to a former Chair of the Authority. It is planted with a cross-section of typical native Dartmoor plants. It also houses some typical Dartmoor archaeological features, such as a 4,000-year-old Bronze Age burial kistvaen (or cist) and a Medieval granite cross from Ter Hill. This marked the Monk's Path but was constantly being pushed over by cattle. The purpose of the Garden is to illustrate the biodiversity on Dartmoor. The project came online in June 2015.

Widecombe telecommunications mast
The DPA were involved in a campaign in June 2015 against four telecommunications masts planned for Dartmoor, with the first to be erected in the village of Widecombe. At short notice, the DPA banners were taken out, letters written, press interviews given and support given to the villagers when an inflatable mast was demonstrated – with the effect that the planning application was withdrawn.

Friends of Dartmoor
In common with other amenity bodies, such as those for the Lake District, Peak District, Pembrokeshire Coast, Yorkshire Dales Three Peaks and the New Forest Trust, the image of Dartmoor Preservation Association is evolving from its Victorian origins, although the original name is being retained. Friends of Dartmoor projects a more modern image of preservation where several years of diplomacy have achieved good relations with the partner agencies that operate in the Dartmoor arena. This is due mainly to the efforts of the previous CEO, James Paxman and his successor, Phil Hutt.

Constitution, objectives and policies
The DPA Constitution, objectives and policies are published on the DPA web site.

The objectives enshrined in the constitution are the protection, preservation and enhancement in the public interest of the landscape, antiquities, flora and fauna, natural beauty, cultural heritage and scientific interest of Dartmoor. Also the protection and preservation of public access to and on Dartmoor subject to the ancient rights of commoners. Co-operation with the commoners and any organisation in achieving DPA objectives, also the study of and the recording and publication of information upon the antiquities, history and natural history of Dartmoor.

The DPA has twenty-two policies listed on its web site: regarding access and rights of way, fencing, protecting monuments, diverse habitats, bracken, china clay quarrying, military training and live firing, hill farming and small scale traditional local industries, quarrying, television and telephone masts, wind farms, planning applications, housing developments, woodlands and forestry, ponies, swaling, and recreational activities.

Conservation
The DPA conservation team meet throughout the year to work on a number of ongoing projects; from gorse clearance, to habitat protection and archaeological surveying. A quarterly timetable is released both on the organisation's website and through its member publications, along with details of how to get involved. The team also host an annual open day at the DPA land holding of Pudsham Meadows.

title: Dartmoor Preservation Association


text:
Talk:Diode

Thermal coefficient of voltage
Could anyone say how do you say in english the phrase corresponding to the ratio of temperature to voltage for a given junction and/or diode? I want to make a bulgarian article with translation of this phrase. I am talking about the positive and negative coefficient/ratio of temperature to voltage for some semiconductor elements. Also how do you call a backward way of the current? When it is used for testing for example on a given circuit you put + to ground and - to + at the source of voltage/current I think. Please also answer on my private discussion page :).--Leonardo Da Vinci (talk) 19:12, 25 March 2011 (UTC)
 * You'd probably find people writing about the "temperature coefficient" of the diode voltage, in English. "Backward" current is usually called "reverse" current in the context of testing diodes; a diode might be rated to carry, say, 10 amperes in the forward direction, but when tested with a reverse or inverse voltage, would show only a very tiny "leakage current" of perhapes a fraction of a microampere; until the voltage got too high, anyway, at which point the diode junction would "break down" and a large current would flow in the reverse direction. Diodes are rated at the "peak inverse voltage" they can withstand in the reverse direction. Does any of this help? --Wtshymanski (talk) 21:13, 25 March 2011 (UTC)

Yes but for ""temperature coefficient" of the diode voltage" maybe you mean only for diodes? The exact voltage is dependant on the temperature. Increasing temperature increases the current/voltage flow in a given electrical device. So this event must have some specific phrase to call it. Something like TCV - Temperature Coefficient of Voltage or something you know ;). It also can be positive and negative depending on the working voltage and diode ;). — Preceding unsigned comment added by Leonardo Da Vinci (talk • contribs) 14:53, 26 March 2011 (UTC)

Unheadered stuff
Does anyone know which type of symbol (DIN 6779 / ISO / IEC / ...) the displayed symbol in the article is? it would be nice to add the comment there... _i_ ^ / \ --- |

Does anyone know how a diode prevents current from flowing in one direction but permits it in the other?

 * For the case of a semiconductor-based diode see the discussion of a p-n junction on the semiconductor page. Someone might want to adapt this for the Diode main page. -- Matt Stoker

In a vacuum diode, the materials of the anode and cathode have different attraction to keep their electrons, the cathode may be pointed to concentrate the electric field and the cathode is usually heated to "boil" off electons. The anode is called the "plate" because it is flat to spread out the field so it is not anywhere strong enough to pull out electrons. Sorry not to include links. I can help find more detail if needed. David R. Ingham 04:44, 7 January 2006 (UTC)

Does the use of galena as a detector (referred to in semiconductor devices) predate the vacuum tube rectifier? - David M
 * The crystal in a crystal radio is a naturally occurring mineral, used as a detector before practical vacuum-tube electronics. (I believe it has a point contact that is at least analogous to the point-contact diode of about 1950 that is the start of the Bell Labs drive toward commercial semiconductor electronics.)  If the crystal of the crystal radio is galena, then the answer to your question is yes. --Jerzy 15:34, 2003 Nov 19 (UTC)

I thought I'd just explain why I changed "current" to "charge". Current doesn't really flow from A to B, but charge does. Just like "water flow rate" doesn't flow anywhere, but the water itself does. --User:Dgrant

 * Arguable. The current revision "they allow an electric current in one direction" doesn't make sense to me. It seems to be missing a verb. "...current to occur..." sounds better to my ear, but can we just call "current flows" common usage? -- Tim Starling

 * Yes, you are right. "to occur" or "to exist" would be the purest form in my opinion, but we can leave it the way it is.  It's quite interesting I was able to find a fair share of both usages on Google.  No doubt "current flowing" is probably more common.  --Dave

It was I who changed "charge" back to "current", but in the light of the comments above, I decided that my version was no more or less correct than the previous one. Now, in an effort to please everybody, I have expanded the definition to mention both charge and current.

I think that the question of whether current "flows" or just "is" is merely a question of style. At worst, I think that "current flows" is harmlessly redundant. -- Heron

 * True. I think I can agree with "harmlessly redundant".  I like the first paragraph now, how it uses singular form "diode" and "it" instead of "diodes" and "they".

 * The phrase "current flows" is harmless only if you already understand electrical physics. For newbies the phrase creates a serious misconception: the wrong idea that "current" is a substance, a substance which can "flow."   This error grows to full-blown proportions in textbooks aimed at kids in grade school.  Authors of these textbooks don't discuss the flow of charges within wires, instead they explain that "current electricity" flows in wires.  An easy way to pop these bubbles of misconceptions is to ruthlessly remove all apparently harmless miswording such as "current flows."   Instead say "charges flow" or "electrons flow" or "electric currents appear," etc. --Wjbeaty 21:07, Apr 14, 2005 (UTC)

 * I agree. Unfortunately, there are many examples of the 'sloppy' use of terminology that, IMHO, hinder the learning process.  I recently began teaching an introductory class in electrical engineering.  In preparing for this class, I came to realize how careless I had become with the terminology of my field.  In the end, my own understanding of the material improved once I began to critically evaluate how I used terms such as current.  Alfred Centauri 14:17, 27 May 2005 (UTC)

Diode vs rectifier
As this is the general 'diode' article, it seems to me that the section on rectification schemes can be moved into rectifier, and the discussion of p-n diode characteristics can be cut down and handled on p-n junction instead. Any thoughts? - mako 05:45, 10 July 2005 (UTC)

Yes, I agree this article is getting confused between rectifier and diode descriptions. After all, many diodes are not in fact used as rectifiers at all. Rectifiers should IMHO be moved to the rectifier article. Alan

 * Good point. Let's split them completely. - Omegatron 05:04, July 31, 2005 (UTC)

 * It seems to me that in its present form the introduction is still confusing diodes with rectifiers. A diode is a device with two terminals. Not all diodes are rectifiers. That's what we learned way back in circuits 101 and that's what it says in Merriam-Webster -"an electronic device that has two electrodes or terminals and is used especially as a rectifier". I'm going to change it to reflect this basic fact that every electrical engineer should know and if anyone wants to change it back to the incorrect definition, please provide a source. Tarchon 20:45, 23 October 2007 (UTC)

Gas discharge diode
I had not heard of this device before. Does it exist? Can anyone refer to an example part or manufacturer or example of useage?? Al

 * I'm pretty sure it exists; I'll look it up when I have time. BTW, thanks for your contribs. Do consider signing up for an account. - mako 21:41, 31 July 2005 (UTC)

 * No evidence on these devices has yet come to light so i have moved the para here for consultation. What think you O? Light current 01:27, 6 August 2005 (UTC)

Gas Discharge Diode : There are two electrodes, not touching, in some kind of gas. One electrode is very sharp. The other has a smoothly curved finish. If a strong negative potential is applied to the sharp electrode, the electric field near the sharp edge or point is enough to cause an electrical discharge in the gas, free carriers are created, and a low resistance path appears. If the reverse potential is applied, the electrical field strength around the smooth electrode is not enough to start a discharge. (The discharge can only start easily at the negative end because electrons are much more mobile than positive ions.) These are sometimes used for high-voltage high-current rectification in power supply applications.

 * Ah, sorry, I should've followed up immediately. According to Electronics by Millman and Seely (1951), there's a whole slew of gas-filled tubes, with various internal structures. I'll have to think about where to put them, though, as some aren't really diodes. (As for the paragraph above, I'm not sure about this "very sharp" electrode etc. business; it'd be enough to say that the tubes operate based on breakdown/ionization. It also seems it's a cold cathode tube. I doubt such things are used anymore, as a significant reverse voltage would also cause conduction.) - mako 05:06, 6 August 2005 (UTC)

 * I believe you are discussing this? 86.146.209.237 (talk) 16:26, 23 June 2020 (UTC)

No V-I curves...?
There are no V-I curves for the different diodes. Perhaps one for the "normal" or rectifier P-N diode and one for the zener/avalanche diodes would be helpful. If there's consensus, I will create the images and insert them into the articles - unless the images have already been created and excluded for some reason. Rohitbd 12:59, 27 September 2005 (UTC)

 * I made one to show negative resistance, which is used in Gunn diode and Tunnel diode. You could base new ones off of that?  Also you should always check Commons before making a new image (I don't do this often enough.)  I don't see any images for this on Commons, though.  — Omegatron 13:43, 27 September 2005 (UTC)
 * I have created the V-I characteristics image of a rectifier diode as below. Please let me know if it is ok. Thank you. Rohitbd 18:25, 27 September 2005 (UTC)

 * Looks good, though some numbers for current would provide useful context. Maybe a title too - "Typical semiconductor diode I-V characteristic", perhaps. - mako 19:50, 27 September 2005 (UTC)
 * We could indicate current values, but IMHO that will lead non-technical readers into believing that the values shown are the factual ones - which is not the case. Currents vary from device to device. The forward turn-on voltage, however, is true for almost all Si/Ge devices and IMO can be included as a fact. PS: I have slightly changed the V-I curve in the reverse bias region. I believe this to be the correct one for a rectifier - the previous one was perhaps more zener-like. Rohitbd 11:07, 28 September 2005 (UTC)
 * A non-technical reader may also assume that the chart is to scale; I just think some context is useful. Perhaps then a note in the caption about typical currents would be appropriate. Also, I have never heard these referred to as "V-I" characteristics. The ordering is always Y-axis, X-axis. Is this opposite (to me) convention common in your experience? - mako 22:00, 28 September 2005 (UTC)
 * Ok...but I do not know (rather remember) what typical current values to use. Maybe you can provide me with some (leakage current, reverse current...?). And "V-I" is perhaps my own "quirk"...maybe I memorised it that way all along - I shall use whatever is the accepted convention - good that I did not add this directly into the image. Rohitbd 07:40, 29 September 2005 (UTC)
 * Looking at the datasheet for a 1N4001, the quoted reverse current is 30 uA. There's no forward leakage parameter; not really a factor when rectifying I suppose. I guess I would say typical current in the off region is on the order of microamps. - mako 00:21, 30 September 2005 (UTC)
 * Added the relevant intormation into the image. Please check if everything is in order and I will link it into the article. Rohitbd 09:48, 30 September 2005 (UTC)

Since no one has objected, I have added the image to the article. Rohitbd 10:08, 5 October 2005 (UTC)
 * I have replaced the image with a vector image. H1voltage (talk) 04:36, 16 January 2009 (UTC)
 * The new image does not include much of the information from the old image. Additionally, both images do not appear to resemble an exponential curve at all. Could someone actually use Shockley diode equation (further down on the page) to generate the curve (above the breakdown region, of course)? —TedPavlic (talk) 14:01, 16 January 2009 (UTC)

The IV curve shown looks pretty symmetric. Forgive my ignorance, I guess this may be true for some types of diode, but the whole point of using a rectifying diode is that the characteristic isn't symmetric. More asymmetry would also help to more clearly identify forward and reverse bias etc...Michi zh (talk) 09:49, 22 July 2011 (UTC)

Suggestions to add to the I-V plot: Get rid of the kink at V=0. Compare ideal with nonideal diodes. Draw it to scale, with an inset to zoom in to show the (tiny!) reverse bias leakage current and the line passing through the origin (I=0 at V=0). I'll add these if I get time, otherwise please Be Bold. Mwistey (talk) 06:04, 14 November 2011 (UTC)

I like the suggestions by talk, but since Nov. 2011 no one implemented them! Here is my contribution: I prepared a SVG figure with the Shockley equation and some realistic parameters. Shall we replace Fig. 5 in the article? Hldsc (talk) 18:19, 9 July 2013 (UTC)

 * I just reverted someone trying to add "Zener" to the caption. The intention of this diagram is not to portray a Zener diode, but rather a general p-n diode.  However, I failed to notice that the drive for this change was that the breakdown voltage is shown as 4 volts.  The editor is quite right that this is entirely unrealistic for a typical diode and the diagram needs adjusting.  The positive and negative voltages could be drawn to different scales, but posssibly a better solution is for a break in the curve.  Show, for instance, -1 V to +1 V and - 40 V to -45 V as two disconnected sections.  Spinning  Spark  10:45, 12 April 2014 (UTC)

 * Sadly, although Hldsc claims they drew this as an svg, they have uploaded it as png. It will have to be redrawn to fix the problem unless the original svg is provided.  Spinning  Spark  10:53, 12 April 2014 (UTC)
 * Hldsc has now supplied me with the svg and I have uploaded a modification.  Spinning Spark  21:15, 12 April 2014 (UTC)

In Zenear diode Avalanche breakdown happen with respect to increase of I amps. Here I am assuming I amps and V volts is in a Bijection function. It means diode couldn't tolerate the I amps which is raised or given in period of time. In that time several spike and surges happens so or while it might that Avalanche happens so. Now lets revisit the Graph, instead of taking I amps units in Y-axis and V volts in X-axis. Lets take the time alone in anyone of the axis, say in Y. Then the way Zenear diode function is can be said as f(x), like a share market graph. When it is plotted f(x) reveals several truths. That can be analyzed in several Metrics and many assertive truthful abstract can be get to known by the fact. NOW say Avalache starts freaks out. F(X) becomes collateral. But assume we formed the powerful Zenear as is so. So f(x) still in assertive metrics. So finally the function T is impacted by some ev (Electron Volt). Now think in such a way that this Zenear Diode is formed for this functionality only. That means the impact say ΔT happens within Zenear. So VLSI and connected systems is as powerful as LHC So, hence this ΔT can impact T.

F(X) == T + ΔT => F(X) == dt.

It reveals, it is just that there exists and can be x=f(y) by holding and reversing Bijection in virtual or in realistic way. Lets form the powerful circuits.–Dev A nand Sadasivamt@lk 11:52, 11 June 2015 (UTC)

types of diodes
i love how the list of diode types is in a completely random order. the descriptions are fine, but it's impossible to quickly find the desired entry. typical "missing the forest for the trees" behavior from wikipedians.

I don't understand the paragraph concerning gold-dopped diodes: gold is supposed to make the diodes operating faster, but the paragraphs ends on the topic of main rectification (i.e very slow operation). Also, it is said that gold-dopped diodes can operate at "signal" speed. Does that mean "high frequency signal"?CyrilB 13:24, 6 March 2006 (UTC)

Thermionic or gaseous state
Is it planed or hoped that gasious state devices will be described here. David R. Ingham 04:46, 7 January 2006 (UTC)
 * I noted that the section previously titled as above (when Mr. Ingham wrote his comment) is now titled: Thermionic and gaseous-state diodes, so there seems to be some confusion over whether "gaseous-state"is just another term for "thermionic" or is a separate and distinct type of diode. There is the concept of gas-filled tubes, but no indication in that article that these are used for diodes.  For example, one gas-filled tube, the thyratron, comes in triode, tetrode and pentode variations, and a krytron has four electrodes.  If there is such a thing as a gas-filled diode, it seems pretty obscure.  On the other hand, I found one source which implies that the term gaseous-state, rather than being a synonym for gas-filled, is a misnomer for vacuum tube, or perhaps implies some early diodes were near-vacuum tubes.  I'm leaning towards the latter interpretation and will update the article accordingly.  If someone knows of actual gas-filled diodes, please update the article with information on them. Wbm1058 (talk) 21:17, 30 November 2011 (UTC)
 * I think you're right; "gaseous state" seems to be used only as an alternative to "solid state". Dicklyon (talk) 21:23, 30 November 2011 (UTC)

Shockley's Diode Equation
Please stop giving Shockley more credit than deserved. He didn't invent the transistor. And, it could easily be argued he didn't invent the BJT. — Preceding unsigned comment added by 74.77.148.238 (talk) 15:43, 8 April 2017 (UTC)

I've heard something about the equation not taking into account "photon recycling effects", which cause the equation to be very inaccurate in the case of photovoltaics. I think this would be significant enough to note on the page. Fresheneesz 21:18, 23 February 2006 (UTC)

 * The Shockley equation is derived with the assumptions that the only processes giving rise to current are drift, diffiusion, and thermal R-G. It ignores photocurrent and R-G center processes.  That's why it's often called the ideal diode equation; R-G center current in the depletion region, series resistance at high forward bias, and reverse breakdown processes are all unaccounted for if you rely only on the Shockley equation. -- uberpenguin

 * Surely the Shockley equation should have its own page? 155.198.202.180 (talk) 09:04, 15 May 2008 (UTC)
 * For the record, Shockley diode equation now has its own page. Em3rgent0rdr (talk) 18:59, 18 January 2023 (UTC)

First Diodes
I always thought the first diodes were point contact diodes, used in crystal sets, but the article claims the first diodes were thermionic. Any references to back the article's claim? Also, my understanding is that the symbol for a diode is actually a drawing of a point contact diode. It has nothign to do with arrows and the direction of current flow. The symbol is polarised as it is because the 'whisker' of a point contact diode is the anode and the flat plate is the cathode. The "arrow" in the diode symbol is really a sharpened needle (whisker) on a flat plate.John Dalton 11:27, 15 March 2006 (UTC)

I agree that the article needs clarifying. I will try to work on it a little. Maybe the confusion is that the first thing called a "diode" was a thermionic tube. Crystals predated vacuum tubes but they were called rectifiers. Today it would be called a Schottky barrier diode. Snafflekid 19:46, 15 March 2006 (UTC)

From the rectifier article: "the difference between the term diode and the term rectifier is merely one of usage, e.g. the term rectifier describes a diode that is being used to convert AC to DC.". The rectifer article goes on to describe the *process* of rectification with passing reference to "point contact rectifiers or crystal detectors". As a *device* crystal diodes/rectifiers seem to have "fallen through the cracks" in that the device itself is outside the scope of the rectifier article and not considered to be a diode in the diode article. Perhaps we are a victim of changing terminology? Crystal (point contact) diodes were originally named by the function they performed. At some point as rectifiers found wider application (possibly corresponding with the invention of the themionic diode??) the name of the function (rectification) and device (diode) seem to have been separated. Possibly this is why themionic diode have gottten the label of "first diodes", as they appeared around the same time as the word "diode" found wider usage? Need to find references to back up this theory!John Dalton 20:25, 15 March 2006 (UTC)

I've added a section on crystal diodes. The article is now internally inconsistent as both thermionic diodes are crystal diodes are claiming to be the first. If I get the time I'll try to fix it, but fel free to jump in before me.John Dalton 21:03, 15 March 2006 (UTC)

The saga continues. I'm not so sure crystal diodes were used before thermionic diodes now. The principle of crystal diodes was discovered in 1874. The principle of thermionic diodes was discovered in 1873. A Thermionic device was patented in 1883, but developed no further. The first practical thermionic diode was patented in 1904. Crystal diodes were in use before then. Maybe I'll just add a 'history' section to the article.John Dalton 21:24, 15 March 2006 (UTC)

Radio demodulation
By my understanding, crystal radios got their name from the crystal in the rectifier, not the quartz crystal in the earphone.John Dalton

I didn't see any reference to a needle and a razor blade?

Yes, the word crystal in the phrase "Crystal Radio" refers to the crystal used in the rectifier. - Tim —Preceding unsigned comment added by 68.249.1.76 (talk) 17:04, 3 November 2009 (UTC)

Question
Would anyone know the reasoning behind placing a diode across the controls of a DC low voltage relay?

 * It's a protection diode. When you switch off the relay coil, the collapsing magnetic field creates a voltage (the back-EMF) much larger than that used to energise it, and of the opposite polarity. This voltage can sometimes be enough to destroy the transistor that controls the relay. The diode soaks up the back-EMF without interfering with the normal operation of the relay. --Heron 20:53, 18 April 2006 (UTC)

 * Not fast enough... I put my explanation, though it is not as good!

 * The magnetic coil of a relay is an inductor, so it is not possible to instantaneously interrupt the current in it. If you try to do so, using a switch or a transistor, the inductor will generate high voltages that can damage or destroy your switch. Placing a diode across the coil provides an alternative circuit to the current (until the inductor is completely discharged), so there is no overvoltage. -- CyrilB 20:58, 18 April 2006 (UTC)

 * I'm considering rewording the "Overvoltage protection" section and possibly renaming it to something more appropriate as i think it might be missleading, especialy to an amateur. the section should realy refrerence inductance with perhaps a wikilink to inductors. i would appreciate peoples thoughts before i change the section. —The preceding unsigned comment was added by Keirstitt (talk • contribs) 10:22, 9 February 2007 (UTC).

There is now an article that talks about exactly this -- flyback diode. So ... should we explain this in both diode and flyback diode ? --75.37.227.177 15:43, 25 July 2007 (UTC)

Radiation Detector
(mostly as a reminder to myself) the section on radiation detection needs clean-up and correction. Unfortunately also the semiconductor detector article is not good, so I can't copy from there. Sergio Ballestrero 23:10, 3 May 2006 (UTC)

Picture Links
I made the titles of the schematic diagrams into links to their respective articles.--24.16.148.75 23:24, 30 June 2006 (UTC)

Manatom
I have removed the obscure line:

Engr.Louriel R. Manatom

I have no idea why it was there; if somebody has an explanation, he's free to offer it. John Reid 07:36, 16 October 2006 (UTC)

Caption
I suggest this be added to the caption. It would make the illustration useful for someone trying to figure out which way a diode goes. The trouble is I'm not sure it's true - can someone who knows, check?

—The preceding unsigned comment was added by 190.56.56.246 (talk) 13:08, 17 April 2007 (UTC).

 * the left one (and now in the article the bottom one) is a bridge rectifier (containing four single diodes), that makes it difficult to find a proper caption for arrow directions. Other types show a band for the cathode terminal, the screw-like ones mostly have the case as cathode terminal.--Ulfbastel 13:32, 26 September 2007 (UTC)

Greek roots
The term "diode" does not come from "two" and "odos". The "di" is from "dia" so "diodos" is "dia-odos", the path through which something passes. On the other hand in William Eccles the story goes that Eccles invented the term Diode to describe an evacuated glass tube containing two electrodes; an anode and a cathode.. However the word doesn't have that meaning in greek, it would be nice if there was a source so we could know what Eccles was really thinking - Badseed 00:48, 27 May 2007 (UTC)

 * The OED says di-, twice, and odos, way. Is it wrong? --Heron 10:52, 27 May 2007 (UTC)

 * Unlikely, but the fact is that that's not what it means in greek. Maybe i got the etymology wrong, I'll dig into it more - Badseed 22:58, 28 May 2007 (UTC)

 * In Greek di in diode comes from dia. I am certain about this, since I'm Greek and study at the Technical University in Athens. Please think about what a diode does: it allows current to pass in a certain direction. So it is a *path* *through* which current passes. And yes Oxford English Dictionary is the definitive dictionary of the English language -no question about that-, but two-way has no real meaning for what a diode does. But as I said, a *path* *through* which current passes in a certain direction tells us definitly what a diode really does -at least in Greek. If di came from two "to describe an evacuated glass tube containing two electrodes", then what does two and path really mean? If an English word is really a Greek Word and this etymology is more logical, then why not accept it? Or at least write both, and give the reader the privilege of choosing?

 * We're not in the business of original research, so unless you can come up with an authoritative source, then the OED version stays. Etymology is based on history, not logic or even meaning.  It doesn't matter whether Eccles got his Greek right or wrong, or even if he made it up on a whim: if he said that he was inspired by those Greek roots, then that, by definition, is the etymology.  Anyway, going back to your logic, maybe he should have called it the "dielectrode", but I think he showed good style by abbreviating it. --Heron 19:43, 8 July 2007 (UTC)

Eccles was honest enough to site the Greek roots of the word diode, only he made an understandable grammatical error, mistaking "δι-" as derived from the word for number "2". Τhe origin is INDEED the word "δίοδος" (pronounced: thEE-o-thos) which exists in the Greek dictionary since ancient times and it means "through passage". It is in fact a compound word, derived from the preposition "διά" (pronounced thee-Ah") and the noun "ὁδός" (pronounced: o-thOs) with the (weaker) vowel "α" dropped in favor of the (stronger) vowel "ο". Τhis is a common grammatical phenomenon in Greek called "elision" in English. The "δι-" is not derived therfore from the word "δύο" (pronounced:thEE-o) because the meaning of the word "δίοδος" does not mean "two paths" but the exact opposite: "One path" [only] between two points. You may consult an English-Greek or (even better) directly a Greek dictionary, if -of course- you possess a good understanding of the [Greek] language. A good starting point would be HERE. BTW, Etymology is indeed based on meaning and logic (and many other things) but not so much in history. It is defined as the study of the origin of words and the way in which their meaning and spelling have changed "throughout" history but is not "based" ON history. Thank you for your attention and you may contact me at the following address if you have any questions: R1100RA@gMail.com.

Meaning of 'diode'
"In electronics, a diode is a two-terminal component,"

You'd expect so from the word derivation, but direct (filament heated) thermionic diodes have 3 terminals. (Similarly, direct heated triodes have 4 terminals.)

For sources for this, see any valve/tube basics text.

The term 'diode' may have originated with a 2 electrode device, but for a century or so, ie almost the entire history of the word, it has been used to describe devices that conduct one way better than the other, and of course some of these are not 2 terminal devices. Tabby (talk) 18:20, 26 November 2007 (UTC)
 * Devices that conduct one way better than the other are rectifiers. Remember the term diode was coined at a time when vacuum tubes were ascendant and semiconductor crystals were rendered (temporarily) obsolete.   di- does mean two and Eccles didn't name the device "diaode".  Another term derived from Greek di- is dipole. Wbm1058
 * diode
 * triode
 * tetrode
 * pentode
 * hexode
 * heptode
 * octode

==

User (Wbm1058) does not possess a solid knowledge of the Greek language, therfore, makes a few erroneous statements. Δι- by it self does not always mean "two". It could also be a derivation from the preposition "διά" as I previously explained. The word for the number two is "δύο". Indeed the word dipole comes from the word "δίπολος" which in Greek is an adjective meaning "having two poles". The etymology is as such: Δύο+πόλος the "o" is dropped, the word becomes δύπολος and for grammatical/spelling reason that go beyond the scope of this the ypsilon "υ" is converted into a iota "i". Finally, δίπολος is the nominative (=ονομαστική) case (=πτώση) but in normal use the word appears in the accusative (=αιτιατική πτώση) e.g. "τον δίπολο" which also very similar but should not be confused with the nominative of the same adjective but in the neutral gender e.g. "το δίπολο".

Finally, Tabby, a resistor is a two terminal component also, is n't it? So is a capacitor, a battery, a rheostat, a coil, a magnet and so forth. I can think of many components with "two-terminals" which -however- are NOT a diode. E.g. having two terminals does not qualify something as a diode. It is the one-way through passage of electrons that give a diode its unique name. Again the di- in diode comes from the preposition "διά" which means (almost verbatim) "through". The di- in dipole on the other hand comes from the number two="δύο", e.g a magnet is indeed a dipole because it is characterized by the presence of TWO poles with opposite ...polarity. Again, please consult an appropriate dictionary, BEFORE you commit into writing inaccurate statements, especially about matters that you possess little or no knolwdge at all. Sincerely, R1100RA@gMail.com

1N numbering
This article is barely more than a stub. No mention of the 1NXXXX numbering system, used for decades as the main way of labelling diodes. No references. No See also or External links.-69.87.199.84 12:38, 20 June 2007 (UTC)

Numbering
A standardized 1N-series numbering system was introduced in the US by EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Among the most popular in this series were: 1N34A/1N270 (Germanium signal), IN914/1N4148 (Silicon signal) and 1N4001-1N4007 (Silicon 1A power rectifier).

"The JEDEC Solid State Technology Association (Once known as the Joint Electron Device Engineering Council), is the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA), a trade association that represents all areas of the electronics industry. JEDEC was originally created in 1960 as a joint activity between EIA an NEMA, to cover the standardization of discrete semiconductor devices and later expanded in 1970 to include integrated circuits."

http://news.elektroda.net/introduction-dates-of-common-transistors-and-diodes-t94332.html http://semiconductormuseum.com/Museum_Index.htm -69.87.199.84 13:34, 20 June 2007 (UTC)

"SemiConducting Diodes" section
There seems to be a small error in this section of the article. The author says that when an electric field is placed across the diode which has the same polarity as the "built -in" electric field, then current is allowed to flow. Assuming that the author is using the conventions of positive charge movement constituting current flow and electric field lines pointing from regions of positive charge to regions of negative then and only then does the reader know what he means when he says that current flows from the P region to the N region. P-type semiconductors are doped with group IIIa atomic elements and N-type semiconductors are doped with group Va atomic elements. On their own they consitute neutral atoms, however, when placed in the silicon lattices of a PN diode electrons move around to form these "built-in" electric fields. The author says that in order for the holes naturally existing in the P region to be filled wiht electrons, electrons must leave the N region to combine with the holes. Being group V elements in the N region, this would leave behind a net positive charge in that region. Conversly, there being group III element in the P region, having these holes filled would create a net negative charge in that region. So we have established that there then should be electric field vectors in the material pointing from the N region to the P region. Since diodes only allow current to flow in the direction of P to N however, placing an electric potential across the diode which has the opposite polarity of the "built-in" field will allow current to flow. This contradicts the statements of the author. Furthermore, you can make sense of this in your mind by thinking of the "built-in" field as a manefestation of the depletion of charge carriers at the interface as the author suggests you do. Then since this built-in field is caused by the device taking on insulating qualities, it would make sense that you should destroy these qualities to allow for conduction of charge: hence placing an electric field across the device with a polarity opposite to that of the "built-in" electric field. 24.248.230.218 16:13, 1 July 2007 (UTC)Ted Cackowski Jr.

hello this will be grate if u give a sketch sectional view of a diod with labeling and from that labeling discribing the specific usage of that part of the object(diode).-rathin dholakia(india)

I wonder if more explicit detail of current flow convention could be described. I am thinking from the perspective of "in the days" of thermionic valves, circuit nomenclature discuss current in terms of electrons (from Cathode to Anode). Its easy to depict the idea of electrons "boiling" off a heated Cathode and flying to the positive charged Anode. However when semiconductors arrived on the scene, circuit nomenclature discussion of current flow became the "conventional" current flow, and so the arrow in the diode symbol depicts the reverse of what would sensibly be the current flow (as in electrons). If someone knows and can write about the history of how this came about, I think would be most appropriate in this diode subject. If I could change history, I would draw the arrow pointing at the Anode, lol! —Preceding unsigned comment added by 124.184.0.98 (talk) 04:20, 20 May 2011 (UTC)

VI curves
Should we show a log-log VI curve? — Omegatron 04:11, 12 September 2007 (UTC)

Question of merge with PIV
In my view the PIV article should be deleted as it is very specific to a particular application, making it misleading the way it is linked in most articles. Brews ohare 19:23, 15 November 2007 (UTC)

I have added an alternative case to the Peak_Inverse_Voltage article that makes it acceptable (in my view). Brews ohare 19:34, 15 November 2007 (UTC)

Appearance
"similar in appearance to incandescent light bulbs"

1920s ones were, but not more modern valves. The shape, metal innards and base are all different to familiar filament bulbs. Tabby (talk) 19:02, 26 November 2007 (UTC)

 * it should note how to tell the difference between signal and germaniums - signal diodes have a black stripe and the germaniums have a green stripe. and are all signal diodes the same? some types are 9v some are 6.7v does this matter?.101.162.139.242 (talk) 09:58, 28 April 2012 (UTC)

Rectifier vs diode
"From the rectifier article: "the difference between the term diode and the term rectifier is merely one of usage, e.g. the term rectifier describes a diode that is being used to convert AC to DC."."

This is incorrect though, there are a number of non-diode devices which have seen use as rectifiers. Commutator and vibrator rectifiers are 2 examples. Tabby (talk) 19:02, 26 November 2007 (UTC)

Guthrie
The article credits Guthrie with discovering thermionic emission. Per the reference, he studied hot metal objects in air. Thomas Edison discovered the unidirectional conductance in a vacuum from a heated filament. This is surely not a "rediscovery" unless Guthrie also used an evacuated tube or globe in his research. Was a hot metal object in air ever used in the vacuum tube era of electronics? Edison (talk) 18:38, 12 December 2007 (UTC)

Reverse recovery time
From the page Reverse recovery time which I have nominated for speedy:
 * Following the end of forward conduction in a diode, reverse current flows for a short time. The device does not attain its full blocking capability until the reverse current ceases.

Bongomatic (talk) 08:23, 23 September 2008 (UTC)

 * I just added a section and stub for the "reverse recovery effect". Mikiemike (talk) 18:39, 5 December 2010 (UTC)

I want to know about the working of Power diode.kindly provide me the topic discription "WORKING OF POWER DIODE". thank you. —Preceding unsigned comment added by 202.157.68.10 (talk) 16:18, 28 July 2009 (UTC)

douse anyone know an example of where a diode is used? —Preceding unsigned comment added by 92.2.17.6 (talk) 21:13, 10 February 2010 (UTC)

Peltier diode
I question if these are actually diodes. Yes, there may be P and N type semiconductor involved, but there is no rectifying junction. --Speedevil (talk) 02:01, 29 September 2010 (UTC)

Added some verbiage clarifying this
--Speedevil (talk) 11:57, 6 October 2010 (UTC)

IV-characteristic / Working principle
The working principle part of the semiconductor diode section repeatedly mentions recombination. However, the recombination of electrons and holes in the semiconductor diode is a parasitic effect and not involved in the device operation at all. The majority carriers leave their respective zone due to the "diffusive forces", i.e. their thermal motion. The majority carriers leave behind their ionized dopands which builds up a field that holds them back and stops the process. Additionally, it seems more reasonable to me to first explain the working principle and then discuss the different types. Etaijoverlap (talk) 22:25, 6 August 2012 (UTC)

 * The focus on recombination does seem like an unusual way to describe it, and I don't see a source cited for it, so if you have a sourced approach that's better, that might be OK. On the other hand, I think it's true that when there's a forward current there needs to be recombination; but not necessarily very quickly.  I don't see how you can invoke diffusion to get a carrier gradient though; diffusion will try to eliminate the gradient, while drift from the fixed dopant charge induced field will try to maintain the gradient.  Dicklyon (talk) 22:50, 6 August 2012 (UTC)

 * Well, in any realistic device there will surely be generation and recombination, but it is not part of the wanted device operation (unless we are talking about LEDs). Generation will lead to an increase in the reverse current and recombination should actually increase the resistance. You can get this quite easily from a standard semiconductor device simulation. I couldn't find this very statement in any published sources but you can look at "Solid State Electronic Devices" by B.G. Streetman or "Physical Models for Semiconductor Devices" by J.E. Carroll. There, the current through the device is basically due to diffusion of minority carriers injected from the respective other side of the space charge region. Regarding your question of how this works without recombination: Imagine you put an n and a p region together. The majority carriers of either side will see a huge gradient at the interface and diffuse. The ionized dopands left behind will then create a field that gets larger as more and more carriers leave their respectively doped area. The process will stop when the diffusive force is balanced by the electric field of the dopands. Still, the diffusion part will try to eliminate the gradient but it will be challenged by the electric field that tries to pull the majority carriers back where they belong. Etaijoverlap (talk) 12:06, 7 August 2012 (UTC)
 * The focus on recombination is one way to describe the characteristics - the description with the electric field is a different one. A possible source that uses recombination as the main step - though possibly not high quality - is here . For doing device modeling from the microscopic parameters this way is the logic one: the saturation current is directly related to recombination live-times. The carriers can only diffuse across the junction if there is a sufficient gradient in concentration - with slow recombination the minority carrier concentration rises so much as to limit the diffusion current. So there are different ways to explain the diode. The preference depends on background and goal.--Ulrich67 (talk) 17:21, 7 August 2012 (UTC)
 * Well, I don't think that recombination and the field are two equivalent descriptions of the device characteristics, as they are completely different physical processes. I agree that the saturation current is determined by recombination, but I see this as a parasitic effect that is happening in parallel to rather than as part of the device operation. It will be necessary to explain the details of realistic IV-curves but is of minor impact to the width of the space charge regions and thus to the rectifying behavior, which I consider the main purpose of the diode. The gradient in the concentration is maintained by the field, see my earlier posts. As a sidenote, also in your reference the width of the space charge region is defined from the depletion approximation, which is based on the electric field. Etaijoverlap (talk) 17:44, 8 August 2012 (UTC)
 * The Calculation with field and space charge is a first step, to get a rough picture of the rectifying behavior, but it does not provide the full IV-characteristics. To get a quantitative IV curve one needs to include the recombination and generation currents, at least for a PN Diode. The electrons flowing in forward direction have to pass the depletion zone and have a recombination event (in the junction or on either side). For PN diodes and much of the IV-curve the recombination (or generation with reverse voltage) is the rate limiting step, not passing the depletion zone. So there is no way to get the correct IV-curve without taking recombination serious. Looking at the field and space charge is more like explaining why the diode can block a relatively high voltage and possibly explain break though. Looking at recombination /generation is the way to calculate the current at a given voltage and also describe dynamic behavior like reverse recovery. As a prerequisite this needs the field in the depletion zone, but here details don't matter: it's not the changing width of the depletion zone that causes the exponential IV curve, but the exponential dependence of minority charge concentration (and thus rate of recombination) on the position of the chemical potential. Taking recombination as the important step, the nonlinear and asymmetric characteristic comes since generation current (revere polarity) is limited to the value at no minority carriers, but recombination current (forward direction) can increase easily just as the minority carrier concentration can increase by orders of magnitude.--Ulrich67 (talk) 19:38, 8 August 2012 (UTC)
 * Quite frankly, this battles my understanding of a diode operation. So what you are saying is that the exponential IV curve of the diode arises from the recombination. Can you give a reference for that? The reference you gave before only states that the recombination gives the same shape but the main behavior comes from the depletion approximation. Etaijoverlap (talk) 21:26, 8 August 2012 (UTC)
 * One important part, responsible for the exponential shape is the assumption that the quasi fermi potentials go right through the depletion region, and thus the formulas for the minority carrier concentrations at the boundary. This is somewhat related to the depletion approximation - as to have the drop in electric potential concentrated at the depletion region. The exact shape of the potential drop or the width of the depletion layer (e.g. in a gradual PN-junction) does not matter.

The second step is than the approximation of a recombination rate proportional to the increase in minority carrier concentrations (thus a constant lifetime). Later the results are written with the diffusion length L instead of carrier lifetime, but these two are related.--Ulrich67 (talk) 16:52, 9 August 2012 (UTC)
 * What do you mean by saying the quasi fermi potentials go "right through" the depletion region? I mean where else are they supposed to go? Could you please try to reformulate your answer? I cannot follow you. — Preceding unsigned comment added by Etaijoverlap (talk • contribs) 22:05, 10 August 2012 (UTC)
 * A reasonable detailed calculation of the I-V curve can be found here: .--Ulrich67 (talk) 20:25, 12 April 2014 (UTC)

Conventional Current Direction in Caption
Can we please stop saying that conventional current (the direction positively charged particles would take) flows out of the cathode? Cathode is n-type (negative-type) and is doped to contain more electrons, so the conventional current would be flowing into this, as the negative charge flows out of it. Stop reverting what is an actually cogent edit. You will confuse people. — Preceding unsigned comment added by 71.200.116.57 (talk) 02:21, 5 January 2013 (UTC)
 * When it is forward biased, majority carriers will flow out of each region into the other, otherwise the diode wouldn't conduct - holes flow out of the p-region into the n-region, and electrons flow out of the n-region into the p-region. Therefore the direction of conventional (positive) current is from the p to n region, and out of the n region into the wire.  The n-region is the cathode, so conventional current flows out of the cathode.   An equivalent way to look at it is that the p-region must be have a positive voltage with respect to the n-region, so (positive) holes will be repelled into the n-region and electrons in the n-region will be attracted into the p-region.  Since the p (anode) region has the positive voltage, electrons will be attracted up the cathode wire into the cathode (n-region) and across the junction into the p-region.  Since electrons (negative charge) are flowing into the cathode, conventional current (positive charge) is flowing out of the cathode.  An easy way to remember it is that forward bias current flows in the direction the diode "arrow" points - from anode to cathode. -- Chetvorno TALK 07:31, 5 January 2013 (UTC)

Two different Zener Diode symbols ?
The "Zener Diode" page has the symbol: http://en.wikipedia.org/wiki/File:Zener_diode_symbol-2.svg

which is quite different to the symbol on the "Diode" page: http://en.wikipedia.org/wiki/File:Zener_diode_symbol.svg

Please would someone knowledgeable add a correction or note to indicate why there is a difference ? Darkman101 (talk) 09:58, 13 May 2013 (UTC)

Threshold Voltage
This article continues the myth that there is a Threshold Voltage in the forward V/I curve, however as the curve is essentially an Exponential, there can be no threshold, ie the rate of change is smooth and continuous, there is no elbow. Draw it on a Log scale and the "elbow" disappears. The idea of an Offset Voltage comes from a simple piece-wise approximation that is taught to students and technicians, but is then taken as gospel. The Threshold Voltage does not in fact exist. Gutta Percha (talk) 06:58, 17 September 2013 (UTC)

Request for Discussion of in electronic articles
Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • Sbmeirow  •  Talk  • 23:36, 15 December 2013 (UTC)

Use of diodes in overdriving and distorting signals in music
Overdrive and/or distortion (clipping) is among the most often employed effects in modern music - particular for guitarists. The effect is overwhelmingly achieved through use of diodes, yet no mention is made of this in the article. The various distortion variations are listed here: http://en.wikipedia.org/wiki/Distortion_%28music%29 but that does not focus on curcuits or components. This article may therefore be a good place for this. 83.249.137.51 (talk) 07:15, 4 March 2014 (UTC)

Unsupported section
The mention of Guthrie in the vacuum tube diodes section contains unsupported and incorrect information. The citations do not support that Guthrie discovered thermionic emmission and the speculation in this section of the Wiki is original and incorrect work by the submitter. Examination of the cited sources will show that Guthrie did not present any conceptual model rising to the level of "principle". The second source cited clearly states that researchers such as Guthrie and others of Guthrie's time did not know the mechanism behind the effects they observed. Specifically they did not know whether some chemical reaction in the air might be responsible or whether some other action may be the cause of their observations. Guthrie was working with static electricity rather than current electricity so did not share any observations regarding current electricity in the cited work. 184.45.6.44 (talk) 16:18, 17 April 2014 (UTC)
 * There seems to be plenty of book sources making this claim.  Spinning Spark  17:37, 17 April 2014 (UTC)

 * 7 June 2018, Vacuum tube history Guthrie, Edison section edited to accurately reflect sources cited in the article. LSMFT (talk) 18:17, 7 June 2018 (UTC)

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1N34 circular reference
A reference to the newworldencyclopedia about the 1N34 diode has been added. However, upon examining the history there, the phrase "still used in radio receivers as a detector and occasionally in specialized analog electronics" that appears there was just copied from this Wikipedia article. Hence it is not a reference to valid source. I'm restoring the "needs reference" template. Constant314 (talk) 21:16, 25 October 2017 (UTC)

The 1N34 germanium diode should have its own article!
I haven't looked to see if Constant314's comment of 2017 is still applicable. But I was surprised to find that Wikipedia doesn't have an article dedicated to either the 1N34 and its variants, or perhaps early germanium diodes more generally. The 1N34 was introduced in 1946, and it was the first commercial germanium diode. I easily found more info such as this link. I don't have time to do more on this, but someone should. Oaklandguy (talk) 02:15, 2 July 2021 (UTC)
 * Why? Is there the remotest chance a random diode will pass the general notability standard? No individual part number is notable on its own. --Wtshymanski (talk) 17:59, 8 July 2021 (UTC)
 * Actually I don't see 1N34 as just a part number, it was THE diode for many years, before silicon diodes became available, and is still used (I do!) especially when you want the low forward voltage drop (like for a crystal radio). And Oaklandguy wanted a page on "1N34 and its variants, or perhaps early germanium diodes more generally" which I agree with (so I don't care about the articles title, just that 1N34 redirects there). But someone else needs to write it. Interferometrist (talk) 19:21, 8 July 2021 (UTC)
 * 1N34 / 1N34A are well-known part numbers to anyone who fixes older equipment. It's a lot more notable than claimed.  https://www.mikeselectronicparts.com/product/1n34a/  •  Sbmeirow  •  Talk  • 06:24, 14 July 2021 (UTC)
 * That's not the general notability guideline though, is it? It's just a part number.  You might as well write an article about a  1/4 inch by 20 TPI stove bolt - I bet there's even more of them out there than 1N34 diodes and they are just as important to the people who restore antique farm machinery. --Wtshymanski (talk) 00:21, 20 July 2021 (UTC)
 * "1/4 inch by 20 TPI stove bolt" is not a part number. •  Sbmeirow  •  Talk  • 04:26, 20 July 2021 (UTC)

I was also quite surprised to learn that the 1N34 did not have its own article. For my blog, I was going to reference it, and as I often do, I did a Google search for "1N34 Wikipedia". Lo and behold, there was no article, but this discussion showed up as the search result.

For an example of a "part number" that has its own article, see the article for the CK722 transistor.

Clemlaw (talk) 01:12, 11 November 2021 (UTC)

Photo needed
How about some pictures of diodes that didn't come from Radio Shack? They go up to 2000 or 3000 amps, but Commons has nothing other than a myriad of painfully drawn schematic symbols and photos of various bitty diodes. We don't need a million more pictures of DO41 cases, the reader surely gets the idea after the first 20 or 30. --Wtshymanski (talk) 22:51, 12 November 2017 (UTC)

Small-signal behavior
Based on the diode equation, I would expect the first derivative term in the Taylor series to be significant. I would expect that the small signal I:V curve would be linear or linear + square. However, in mixer and detector applications, the linear term may be unimportant since it produces harmonics at the fundamental which may be filtered out. Anyway, I think the statement that the I:V curve is square law needs some clarification. Constant314 (talk) 18:54, 7 June 2018 (UTC)

 * I agree; it should be made clear in that section that "square law" is an approximation to the actual exponential curve which is only valid over small signal levels. It is the 2nd order term (2nd derivative, coefficient of v2) in the Taylor expansion which is significant and produces the difference frequencies which form the audio output; I think that is what you meant. The first order term (linear term or first derivative, coefficient of v) just produces components in the output at the original frequencies.  The "square law" approximation is obtained by truncating the Taylor series after the 2nd order term: $$i \approx A_0 + A_1 v + A_2 v^2$$ --ChetvornoTALK 19:24, 7 June 2018 (UTC)
 * Yes. I think the missing information is that a detector or mixer application is assumed.Constant314 (talk) 19:53, 7 June 2018 (UTC)

 * Editors Chetvorno, Constant314, thank you for your illuminating notes - I edited the section, hopefully it is improved. Please add or change as you see fit. LSMFT (talk) 15:44, 8 June 2018 (UTC)

 * Please check the reference to see if zero bias is assumed.Constant314 (talk) 17:05, 8 June 2018 (UTC)

Reduce "Shockley diode equation" section and just point to Shockley diode equation
I would suggest removing all discussion in out of this article and instead merge it into its dedicated page Shockley diode equation. The most this page's section on it should provide is writing out the equation and identifying the names of variables and maybe including a thumbnail picture, and maybe mention that details can be found in Shockley diode equation page. Em3rgent0rdr (talk) 19:05, 18 January 2023 (UTC)

 * It's been over 24 hours, and I haven't heard any objections, so I've went ahead and cut it down to just one sentence and am telling readers to visit Shockley diode equation for details. Em3rgent0rdr (talk) 03:29, 19 January 2023 (UTC)

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Talk:Dartmouth/old article history

The history for the page that used to be located at Dartmouth.

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