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Bipolar junction transistor

A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current flowing between the terminals, making the device capable of amplification or switching.

BJTs use two p–n junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. The superior predictability and performance of junction transistors quickly displaced the original point-contact transistor. Diffused transistors, along with other components, are elements of integrated circuits for analog and digital functions. Hundreds of bipolar junction transistors can be made in one circuit at very low cost.

Bipolar transistor integrated circuits were the main active devices of a generation of mainframe and minicomputers, but most computer systems now use Complementary metal–oxide–semiconductor (CMOS) integrated circuits relying on the field-effect transistor (FET). Bipolar transistors are still used for amplification of signals, switching, and in mixed-signal integrated circuits using BiCMOS. Specialized types are used for high voltage switches, for radio-frequency (RF) amplifiers, or for switching high currents.

Current direction conventions
By convention, the direction of current on diagrams is shown as the direction that a positive charge would move. This is called conventional current. However, current in metal conductors is generally due to the flow of electrons. Because electrons carry a negative charge, they move in the direction opposite to conventional current. On the other hand, inside a bipolar transistor, currents can be composed of both positively charged holes and negatively charged electrons. In this article, current arrows are shown in the conventional direction, but labels for the movement of holes and electrons show their actual direction inside the transistor.

Arrow direction
The arrow on the symbol for bipolar transistors indicates the p–n junction between base and emitter and points in the direction in which conventional current travels.

Function
BJTs exist as PNP and NPN types, based on the doping types of the three main terminal regions. An NPN transistor comprises two semiconductor junctions that share a thin p-doped region, and a PNP transistor comprises two semiconductor junctions that share a thin n-doped region. N-type means doped with impurities (such as phosphorus or arsenic) that provide mobile electrons, while p-type means doped with impurities (such as boron) that provide holes that readily accept electrons.

Charge flow in a BJT is due to diffusion of charge carriers (electrons and holes) across a junction between two regions of different charge carrier concentration. The regions of a BJT are called emitter, base, and collector. A discrete transistor has three leads for connection to these regions. Typically, the emitter region is heavily doped compared to the other two layers, and the collector is doped more lightly (typically ten times lighter ) than the base. By design, most of the BJT collector current is due to the flow of charge carriers injected from a heavily doped emitter into the base where they are minority carriers (electrons in NPNs, holes in PNPs) that diffuse toward the collector, so BJTs are classified as minority-carrier devices.

In typical operation, the base–emitter junction is forward biased, which means that the p-doped side of the junction is at a more positive potential than the n-doped side, and the base–collector junction is reverse biased. When forward bias is applied to the base–emitter junction, the equilibrium between the thermally generated carriers and the repelling electric field of the emitter depletion region is disturbed. This allows thermally excited carriers (electrons in NPNs, holes in PNPs) to inject from the emitter into the base region. These carriers create a diffusion current through the base from the region of high concentration near the emitter toward the region of low concentration near the collector.

To minimize the fraction of carriers that recombine before reaching the collector–base junction, the transistor's base region must be thin enough that carriers can diffuse across it in much less time than the semiconductor's minority-carrier lifetime. Having a lightly doped base ensures recombination rates are low. In particular, the thickness of the base must be much less than the diffusion length of the carriers. The collector–base junction is reverse-biased, and so negligible carrier injection occurs from the collector to the base, but carriers that are injected into the base from the emitter, and diffuse to reach the collector–base depletion region, are swept into the collector by the electric field in the depletion region. The thin shared base and asymmetric collector–emitter doping are what differentiates a bipolar transistor from two separate diodes connected in series.

Voltage, current, and charge control
The collector–emitter current can be viewed as being controlled by the base–emitter current (current control), or by the base–emitter voltage (voltage control). These views are related by the current–voltage relation of the base–emitter junction, which is the usual exponential current–voltage curve of a p–n junction (diode).

The explanation for collector current is the concentration gradient of minority carriers in the base region. Due to low-level injection (in which there are much fewer excess carriers than normal majority carriers) the ambipolar transport rates (in which the excess majority and minority carriers flow at the same rate) is in effect determined by the excess minority carriers.

Detailed transistor models of transistor action, such as the Gummel–Poon model, account for the distribution of this charge explicitly to explain transistor behaviour more exactly. The charge-control view easily handles phototransistors, where minority carriers in the base region are created by the absorption of photons, and handles the dynamics of turn-off, or recovery time, which depends on charge in the base region recombining. However, because base charge is not a signal that is visible at the terminals, the current- and voltage-control views are generally used in circuit design and analysis.

In analog circuit design, the current-control view is sometimes used because it is approximately linear. That is, the collector current is approximately $$\beta_\text{F}$$ times the base current. Some basic circuits can be designed by assuming that the base–emitter voltage is approximately constant and that collector current is β times the base current. However, to accurately and reliably design production BJT circuits, the voltage-control model (e.g. the Ebers–Moll model) is required. The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modeled as a transconductance, as in the Ebers–Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred. For translinear circuits, in which the exponential I–V curve is key to the operation, the transistors are usually modeled as voltage-controlled current sources whose transconductance is proportional to their collector current. In general, transistor-level circuit analysis is performed using SPICE or a comparable analog-circuit simulator, so mathematical model complexity is usually not of much concern to the designer, but a simplified view of the characteristics allows designs to be created following a logical process.

Turn-on, turn-off, and storage delay
Bipolar transistors, and particularly power transistors, have long base-storage times when they are driven into saturation; the base storage limits turn-off time in switching applications. A Baker clamp can prevent the transistor from heavily saturating, which reduces the amount of charge stored in the base and thus improves switching time.

Transistor characteristics: alpha ($α$) and beta ($β$)
The proportion of carriers able to cross the base and reach the collector is a measure of the BJT efficiency. The heavy doping of the emitter region and light doping of the base region causes many more electrons to be injected from the emitter into the base than holes to be injected from the base into the emitter. A thin and lightly doped base region means that most of the minority carriers that are injected into the base will diffuse to the collector and not recombine.

Common-emitter current gain
The common-emitter current gain is represented by $β$F or the $h$-parameter $h$FE; it is approximately the ratio of the collector's direct current to the base's direct current in forward-active region. (The F subscript is used to indicate the forward-active mode of operation.) It is typically greater than 50 for small-signal transistors, but can be smaller in transistors designed for high-power applications. Both injection efficiency and recombination in the base reduce the BJT gain.

Common-base current gain
Another useful characteristic is the common-base current gain, $α$F. The common-base current gain is approximately the gain of current from emitter to collector in the forward-active region. This ratio usually has a value close to unity; between 0.980 and 0.998. It is less than unity due to recombination of charge carriers as they cross the base region.

Alpha and beta are related by the following identities:
 * $$\begin{align}

\alpha_\text{F} &= \frac{I_\text{C}}{I_\text{E}}, & \beta_\text{F} &= \frac{I_\text{C}}{I_\text{B}}, \\ \alpha_\text{F} &= \frac{\beta_\text{F}}{1 + \beta_\text{F}} & \iff \beta_\text{F} &= \frac{\alpha_\text{F}}{1 - \alpha_\text{F}}. \end{align}$$

Beta is a convenient figure of merit to describe the performance of a bipolar transistor, but is not a fundamental physical property of the device. Bipolar transistors can be considered voltage-controlled devices (fundamentally the collector current is controlled by the base–emitter voltage; the base current could be considered a defect and is controlled by the characteristics of the base–emitter junction and recombination in the base). In many designs beta is assumed high enough so that base current has a negligible effect on the circuit. In some circuits (generally switching circuits), sufficient base current is supplied so that even the lowest beta value a particular device may have will still allow the required collector current to flow.

Structure

BJTs consists of three differently doped semiconductor regions: the emitter region, the base region and the collector region. These regions are, respectively, p type, n type and p type in a PNP transistor, and n type, p type and n type in an NPN transistor. Each semiconductor region is connected to a terminal, appropriately labeled: emitter (E), base (B) and collector (C).

The base is physically located between the emitter and the collector and is made from lightly doped, high-resistivity material. The collector surrounds the emitter region, making it almost impossible for the electrons injected into the base region to escape without being collected, thus making the resulting value of α very close to unity, and so, giving the transistor a large β. A cross-section view of a BJT indicates that the collector–base junction has a much larger area than the emitter–base junction.

The bipolar junction transistor, unlike other transistors, is usually not a symmetrical device. This means that interchanging the collector and the emitter makes the transistor leave the forward active mode and start to operate in reverse mode. Because the transistor's internal structure is usually optimized for forward-mode operation, interchanging the collector and the emitter makes the values of α and β in reverse operation much smaller than those in forward operation; often the α of the reverse mode is lower than 0.5. The lack of symmetry is primarily due to the doping ratios of the emitter and the collector. The emitter is heavily doped, while the collector is lightly doped, allowing a large reverse bias voltage to be applied before the collector–base junction breaks down. The collector–base junction is reverse biased in normal operation. The reason the emitter is heavily doped is to increase the emitter injection efficiency: the ratio of carriers injected by the emitter to those injected by the base. For high current gain, most of the carriers injected into the emitter–base junction must come from the emitter.

The low-performance "lateral" bipolar transistors sometimes used in CMOS processes are sometimes designed symmetrically, that is, with no difference between forward and backward operation.

Small changes in the voltage applied across the base–emitter terminals cause the current between the emitter and the collector to change significantly. This effect can be used to amplify the input voltage or current. BJTs can be thought of as voltage-controlled current sources, but are more simply characterized as current-controlled current sources, or current amplifiers, due to the low impedance at the base.

Early transistors were made from germanium but most modern BJTs are made from silicon. A significant minority are also now made from gallium arsenide, especially for very high speed applications (see HBT, below).

The heterojunction bipolar transistor (HBT) is an improvement of the BJT that can handle signals of very high frequencies up to several hundred GHz. It is common in modern ultrafast circuits, mostly RF systems.

Two commonly used HBTs are silicon–germanium and aluminum gallium arsenide, though a wide variety of semiconductors may be used for the HBT structure. HBT structures are usually grown by epitaxy techniques like MOCVD and MBE.

Regions of operation
Bipolar transistors have four distinct regions of operation, defined by BJT junction biases:
 * Forward-active (or simply active) : The base–emitter junction is forward biased and the base–collector junction is reverse biased. Most bipolar transistors are designed to afford the greatest common-emitter current gain, βF, in forward-active mode. If this is the case, the collector–emitter current is approximately proportional to the base current, but many times larger, for small base current variations.
 * Reverse-active (or inverse-active or inverted) : By reversing the biasing conditions of the forward-active region, a bipolar transistor goes into reverse-active mode. In this mode, the emitter and collector regions switch roles. Because most BJTs are designed to maximize current gain in forward-active mode, the βF in inverted mode is several times smaller (2–3 times for the ordinary germanium transistor). This transistor mode is seldom used, usually being considered only for failsafe conditions and some types of bipolar logic. The reverse bias breakdown voltage to the base may be an order of magnitude lower in this region.
 * Saturation : With both junctions forward biased, a BJT is in saturation mode and facilitates high current conduction from the emitter to the collector (or the other direction in the case of NPN, with negatively charged carriers flowing from emitter to collector). This mode corresponds to a logical "on", or a closed switch.
 * Cut-off : In cut-off, biasing conditions opposite of saturation (both junctions reverse biased) are present. There is very little current, which corresponds to a logical "off", or an open switch.

Although these regions are well defined for sufficiently large applied voltage, they overlap somewhat for small (less than a few hundred millivolts) biases. For example, in the typical grounded-emitter configuration of an NPN BJT used as a pulldown switch in digital logic, the "off" state never involves a reverse-biased junction because the base voltage never goes below ground; nevertheless the forward bias is close enough to zero that essentially no current flows, so this end of the forward active region can be regarded as the cutoff region.

Active-mode transistors in circuits

The diagram shows a schematic representation of an NPN transistor connected to two voltage sources. (The same description applies to a PNP transistor with reversed directions of current flow and applied voltage.) This applied voltage causes the lower p–n junction to become forward biased, allowing a flow of electrons from the emitter into the base. In active mode, the electric field existing between base and collector (caused by VCE) will cause the majority of these electrons to cross the upper p–n junction into the collector to form the collector current IC. The remainder of the electrons recombine with holes, the majority carriers in the base, making a current through the base connection to form the base current, IB. As shown in the diagram, the emitter current, IE, is the total transistor current, which is the sum of the other terminal currents, (i.e. IE = IB + IC).

In the diagram, the arrows representing current point in the direction of conventional current – the flow of electrons is in the opposite direction of the arrows because electrons carry negative electric charge. In active mode, the ratio of the collector current to the base current is called the DC current gain. This gain is usually 100 or more, but robust circuit designs do not depend on the exact value (for example see op-amp). The value of this gain for DC signals is referred to as $$h_{\text{FE}}$$, and the value of this gain for small signals is referred to as $$h_{\text{fe}}$$. That is, when a small change in the currents occurs, and sufficient time has passed for the new condition to reach a steady state $$h_{\text{fe}}$$ is the ratio of the change in collector current to the change in base current. The symbol $$\beta$$ is used for both $$h_{\text{FE}}$$ and $$h_{\text{fe}}$$.

The emitter current is related to $$V_{\text{BE}}$$ exponentially. At room temperature, an increase in $$V_{\text{BE}}$$ by approximately 60 mV increases the emitter current by a factor of 10. Because the base current is approximately proportional to the collector and emitter currents, they vary in the same way.

History
The bipolar point-contact transistor was invented in December 1947 at the Bell Telephone Laboratories by John Bardeen and Walter Brattain under the direction of William Shockley. The junction version known as the bipolar junction transistor (BJT), invented by Shockley in 1948, was for three decades the device of choice in the design of discrete and integrated circuits. Nowadays, the use of the BJT has declined in favor of CMOS technology in the design of digital integrated circuits. The incidental low performance BJTs inherent in CMOS ICs, however, are often utilized as bandgap voltage reference, silicon bandgap temperature sensor and to handle electrostatic discharge.

Germanium transistors
The germanium transistor was more common in the 1950s and 1960s but has a greater tendency to exhibit thermal runaway. Since germanium p-n junctions have a lower forward bias than silicon, germanium transistors turn on at lower voltage.

Early manufacturing techniques
Various methods of manufacturing bipolar transistors were developed.

 * Point-contact transistor – first transistor ever constructed (December 1947), a bipolar transistor, limited commercial use due to high cost and noise.
 * Tetrode point-contact transistor – Point-contact transistor having two emitters. It became obsolete in the middle 1950s.
 * Junction transistors
 * Grown-junction transistor – first bipolar junction transistor made. Invented by William Shockley at Bell Labs on June 23, 1948. Patent filed on June 26, 1948.
 * Alloy-junction transistor – emitter and collector alloy beads fused to base. Developed at General Electric and RCA in 1951.
 * Micro-alloy transistor (MAT) – high-speed type of alloy junction transistor. Developed at Philco.
 * Micro-alloy diffused transistor (MADT) – high-speed type of alloy junction transistor, speedier than MAT, a diffused-base transistor. Developed at Philco.
 * Post-alloy diffused transistor (PADT) – high-speed type of alloy junction transistor, speedier than MAT, a diffused-base transistor. Developed at Philips.
 * Tetrode transistor – high-speed variant of grown-junction transistor or alloy junction transistor with two connections to base.
 * Surface-barrier transistor – high-speed metal-barrier junction transistor. Developed at Philco in 1953.
 * Drift-field transistor – high-speed bipolar junction transistor. Invented by Herbert Kroemer  at the Central Bureau of Telecommunications Technology of the German Postal Service, in 1953.
 * Spacistor – around 1957.
 * Diffusion transistor – modern type bipolar junction transistor. Prototypes developed at Bell Labs in 1954.
 * Diffused-base transistor – first implementation of diffusion transistor.
 * Mesa transistor – developed at Texas Instruments in 1957.
 * Planar transistor – the bipolar junction transistor that made mass-produced monolithic integrated circuits possible. Developed by Jean Hoerni at Fairchild in 1959.
 * Epitaxial transistor –  a bipolar junction transistor made using vapor-phase deposition. See Epitaxy. Allows very precise control of doping levels and gradients.

Theory and modeling

BJTs can be thought of as two diodes (p–n junctions) sharing a common region that minority carriers can move through. A PNP BJT will function like two diodes that share an N-type cathode region, and the NPN like two diodes sharing a P-type anode region. Connecting two diodes with wires will not make a BJT, since minority carriers will not be able to get from one p–n junction to the other through the wire.

Both types of BJT function by letting a small current input to the base control an amplified output from the collector. The result is that the BJT makes a good switch that is controlled by its base input. The BJT also makes a good amplifier, since it can multiply a weak input signal to about 100 times its original strength. Networks of BJTs are used to make powerful amplifiers with many different applications.

In the discussion below, focus is on the NPN BJT. In what is called active mode, the base–emitter voltage $$V_{\text{BE}}$$ and collector–base voltage $$V_{\text{CB}}$$ are positive, forward biasing the emitter–base junction and reverse-biasing the collector–base junction. In this mode, electrons are injected from the forward biased n-type emitter region into the p-type base where they diffuse as minority carriers to the reverse-biased n-type collector and are swept away by the electric field in the reverse-biased collector–base junction.

For an illustration of forward and reverse bias, see semiconductor diodes.

Large-signal models
In 1954, Jewell James Ebers and John L. Moll introduced their mathematical model of transistor currents:

Ebers–Moll model

The DC emitter and collector currents in active mode are well modeled by an approximation to the Ebers–Moll model:

 * $$\begin{align}

I_\text{E} &= I_\text{ES} \left(e^\frac{V_\text{BE}}{V_\text{T}} - 1\right) \\ I_\text{C} &= \alpha_\text{F} I_\text{E} \\ I_\text{B} &= \left(1 - \alpha_\text{F}\right) I_\text{E} \end{align}$$

The base internal current is mainly by diffusion (see Fick's law) and

 * $$J_{n\,(\text{base})} = \frac{1}{W} q D_n n_{bo} e^{\frac{V_\text{EB}}{V_\text{T}}}$$

where
 * $$V_{\text{T}}$$ is the thermal voltage $$kT/q$$ (approximately 26 mV at 300 K ≈ room temperature).
 * $$I_{\text{E}}$$ is the emitter current
 * $$I_{\text{C}}$$ is the collector current
 * $$\alpha_\text{F}$$ is the common base forward short-circuit current gain (0.98 to 0.998)
 * $$I_{\text{ES}}$$ is the reverse saturation current of the base–emitter diode (on the order of 10−15 to 10−12 amperes)
 * $$V_{\text{BE}}$$ is the base–emitter voltage
 * $$D_n$$ is the diffusion constant for electrons in the p-type base
 * W is the base width

The $$\alpha$$ and forward $$\beta$$ parameters are as described previously. A reverse $$\beta$$ is sometimes included in the model.

The unapproximated Ebers–Moll equations used to describe the three currents in any operating region are given below. These equations are based on the transport model for a bipolar junction transistor.

 * $$\begin{align}

i_{\text{C}} &= I_\text{S} \left[                  \left(e^\frac{V_\text{BE}}{V_\text{T}} - e^\frac{V_\text{BC}}{V_\text{T}}\right) - \frac{1}{\beta_\text{R}} \left(e^\frac{V_\text{BC}}{V_\text{T}} - 1\right) \right]\\ i_{\text{B}} &= I_\text{S} \left[ \frac{1}{\beta_\text{F}} \left(e^\frac{V_\text{BE}}{V_\text{T}} - 1                              \right) + \frac{1}{\beta_\text{R}} \left(e^\frac{V_\text{BC}}{V_\text{T}} - 1\right) \right]\\ i_{\text{E}} &= I_\text{S} \left[                  \left(e^\frac{V_\text{BE}}{V_\text{T}} - e^\frac{V_\text{BC}}{V_\text{T}}\right) + \frac{1}{\beta_\text{F}} \left(e^\frac{V_\text{BE}}{V_\text{T}} - 1\right) \right] \end{align}$$

where
 * $$i_\text{C}$$ is the collector current
 * $$i_\text{B}$$ is the base current
 * $$i_\text{E}$$ is the emitter current
 * $$\beta_\text{F}$$ is the forward common emitter current gain (20 to 500)
 * $$\beta_\text{R}$$ is the reverse common emitter current gain (0 to 20)
 * $$I_\text{S}$$ is the reverse saturation current (on the order of 10−15 to 10−12 amperes)
 * $$V_\text{T}$$ is the thermal voltage (approximately 26 mV at 300 K ≈ room temperature).
 * $$V_\text{BE}$$ is the base–emitter voltage
 * $$V_\text{BC}$$ is the base–collector voltage

Base-width modulation

As the collector–base voltage ($$V_\text{CB} = V_\text{CE} - V_\text{BE}$$) varies, the collector–base depletion region varies in size. An increase in the collector–base voltage, for example, causes a greater reverse bias across the collector–base junction, increasing the collector–base depletion region width, and decreasing the width of the base. This variation in base width often is called the Early effect after its discoverer James M. Early.

Narrowing of the base width has two consequences:
 * There is a lesser chance for recombination within the "smaller" base region.
 * The charge gradient is increased across the base, and consequently, the current of minority carriers injected across the emitter junction increases.

Both factors increase the collector or "output" current of the transistor in response to an increase in the collector–base voltage.

Punchthrough
When the base–collector voltage reaches a certain (device-specific) value, the base–collector depletion region boundary meets the base–emitter depletion region boundary. When in this state the transistor effectively has no base. The device thus loses all gain when in this state.

Gummel–Poon charge-control model
The Gummel–Poon model is a detailed charge-controlled model of BJT dynamics, which has been adopted and elaborated by others to explain transistor dynamics in greater detail than the terminal-based models typically do. This model also includes the dependence of transistor $$\beta$$-values upon the direct current levels in the transistor, which are assumed current-independent in the Ebers–Moll model.

Hybrid-pi model

The hybrid-pi model is a popular circuit model used for analyzing the small signal and AC behavior of bipolar junction and field effect transistors. Sometimes it is also called Giacoletto model because it was introduced by L.J. Giacoletto in 1969. The model can be quite accurate for low-frequency circuits and can easily be adapted for higher-frequency circuits with the addition of appropriate inter-electrode capacitances and other parasitic elements.

h-parameter model

Another model commonly used to analyze BJT circuits is the h-parameter model, also known as the hybrid equivalent model, closely related to the hybrid-pi model and the y-parameter two-port, but using input current and output voltage as independent variables, rather than input and output voltages. This two-port network is particularly suited to BJTs as it lends itself easily to the analysis of circuit behaviour, and may be used to develop further accurate models. As shown, the term x in the model represents a different BJT lead depending on the topology used. For common-emitter mode the various symbols take on the specific values as:
 * Terminal 1, base
 * Terminal 2, collector
 * Terminal 3 (common), emitter; giving x to be e
 * ii, base current (ib)
 * io, collector current (ic)
 * Vin, base-to-emitter voltage (VBE)
 * Vo, collector-to-emitter voltage (VCE)

and the h-parameters are given by:
 * hix = hie for the common-emitter configuration, the input impedance of the transistor (corresponding to the base resistance rpi).
 * hrx = hre, a reverse transfer relationship, it represents the dependence of the transistor's (input) IB–VBE curve on the value of (output) VCE. It is usually very small and is often neglected (assumed to be zero) at DC.
 * hfx = hfe, the "forward" current-gain of the transistor, sometimes written h21. This parameter, with lower case "fe" to imply small signal (AC) gain, or more often with capital letters for "FE" (specified as hFE) to mean the "large signal" or DC current-gain (βDC or often simply β), is one of the main parameters in datasheets, and may be given for a typical collector current and voltage or plotted as a function of collector current. See below.
 * hox = 1/hoe, the output impedance of transistor. The parameter hoe usually corresponds to the output admittance of the bipolar transistor and has to be inverted to convert it to an impedance.

As shown, the h-parameters have lower-case subscripts and hence signify AC conditions or analyses. For DC conditions they are specified in upper-case. For the CE topology, an approximate h-parameter model is commonly used which further simplifies the circuit analysis. For this the hoe and hre parameters are neglected (that is, they are set to infinity and zero, respectively). The h-parameter model as shown is suited to low-frequency, small-signal analysis. For high-frequency analyses the inter-electrode capacitances that are important at high frequencies must be added.

Etymology of hFE
The h refers to its being an h-parameter, a set of parameters named for their origin in a hybrid equivalent circuit model (see above). As with all h parameters, the choice of lower case or capitals for the letters that follow the "h" is significant; lower-case signifies "small signal" parameters, that is, the slope the particular relationship; upper-case letters imply "large signal" or DC values, the ratio of the voltages or currents. In the case of the very often used hFE: So hFE (or hFE) refers to the (total; DC) collector current divided by the base current, and is dimensionless. It is a parameter that varies somewhat with collector current, but is often approximated as a constant; it is normally specified at a typical collector current and voltage, or graphed as a function of collector current.
 * F is from Forward current amplification also called the current gain.
 * E refers to the transistor operating in a common Emitter (CE) configuration.

Had capital letters not been used for used in the subscript, i.e. if it were written hfe the parameter indicate small signal (AC) current gain, i.e. the slope of the Collector current versus Base current graph at a given point, which is often close to the hFE value unless the test frequency is high.

Industry models
The Gummel–Poon SPICE model is often used, but it suffers from several limitations. For instance, reverse breakdown of the base–emitter diode is not captured by the SGP (SPICE Gummel–Poon) model, neither are thermal effects (self-heating) or quasi-saturation. These have been addressed in various more advanced models which either focus on specific cases of application (Mextram, HICUM, Modella) or are designed for universal usage (VBIC).

Applications
The BJT remains a device that excels in some applications, such as discrete circuit design, due to the very wide selection of BJT types available, and because of its high transconductance and output resistance compared to MOSFETs.

The BJT is also the choice for demanding analog circuits, especially for very-high-frequency applications, such as radio-frequency circuits for wireless systems.

High-speed digital logic
Emitter-coupled logic (ECL) use BJTs.

Bipolar transistors can be combined with MOSFETs in an integrated circuit by using a BiCMOS process of wafer fabrication to create circuits that take advantage of the application strengths of both types of transistor.

Amplifiers
The transistor parameters α and β characterize the current gain of the BJT. It is this gain that allows BJTs to be used as the building blocks of electronic amplifiers. The three main BJT amplifier topologies are:
 * Common emitter
 * Common base
 * Common collector

Temperature sensors
Because of the known temperature and current dependence of the forward-biased base–emitter junction voltage, the BJT can be used to measure temperature by subtracting two voltages at two different bias currents in a known ratio.

Logarithmic converters
Because base–emitter voltage varies as the logarithm of the base–emitter and collector–emitter currents, a BJT can also be used to compute logarithms and anti-logarithms. A diode can also perform these nonlinear functions but the transistor provides more circuit flexibility.

Avalanche pulse generators
Transistors may be deliberately made with a lower collector to emitter breakdown voltage than the collector to base breakdown voltage. If the emitter–base junction is reverse biased the collector emitter voltage may be maintained at a voltage just below breakdown. As soon as the base voltage is allowed to rise, and current flows avalanche occurs and impact ionization in the collector base depletion region rapidly floods the base with carriers and turns the transistor fully on. So long as the pulses are short enough and infrequent enough that the device is not damaged, this effect can be used to create very sharp falling edges.

Special avalanche transistor devices are made for this application.

Vulnerabilities
Exposure of the transistor to ionizing radiation causes radiation damage. Radiation causes a buildup of 'defects' in the base region that act as recombination centers. The resulting reduction in minority carrier lifetime causes gradual loss of gain of the transistor.

Transistors have "maximum ratings", including power ratings (essentially limited by self-heating), maximum collector and base currents (both continuous/DC ratings and peak), and breakdown voltage ratings, beyond which the device may fail or at least perform badly.

In addition to normal breakdown ratings of the device, power BJTs are subject to a failure mode called secondary breakdown, in which excessive current and normal imperfections in the silicon die cause portions of the silicon inside the device to become disproportionately hotter than the others. The electrical resistivity of doped silicon, like other semiconductors, has a negative temperature coefficient, meaning that it conducts more current at higher temperatures. Thus, the hottest part of the die conducts the most current, causing its conductivity to increase, which then causes it to become progressively hotter again, until the device fails internally. The thermal runaway process associated with secondary breakdown, once triggered, occurs almost instantly and may catastrophically damage the transistor package.

If the emitter–base junction is reverse biased into avalanche or Zener mode and charge flows for a short period of time, the current gain of the BJT may be permanently degraded, as the emitter is smaller than the collector and cannot dissipate significant power. This is a common ESD failure mechanism in low-voltage devices.

title: Bipolar junction transistor


text:
Doping

Doping may refer to:

 * Doping, adding a dopant to something
 * Doping (semiconductor), intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties
 * Aircraft dope, a lacquer that is applied to fabric-covered aircraft
 * Link doping, in search engine optimization

Sports

 * Doping in sport, the use of drugs or other methods to improve athletic performance
 * Abortion doping, the rumoured practice of purposely inducing pregnancy for performance-enhancing benefits, then aborting
 * Blood doping, boosting the number of red blood cells in the bloodstream
 * Boosting (doping), a method of inducing autonomic dysreflexia
 * Gene doping, the hypothetical non-therapeutic use of gene therapy by athletes
 * Stem cell doping
 * Technology doping
 * Doping in China
 * Doping in Russia

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Doping


text:
Trucker's hitch

The trucker's hitch is a compound knot commonly used for securing loads on trucks or trailers. The general arrangement, using loops and turns in the rope itself to form a crude block and tackle, has long been used to tension lines and is known by multiple names. Knot author Geoffrey Budworth claims the knot can be traced back to the days when carters and hawkers used horse-drawn conveyances to move their wares from place to place.

Variations
The portion of the trucker's hitch which differs in the following variations is the method used to form the loop which the working end slides through to produce the mechanical advantage. The different methods of forming the loop affect the ease and speed of tying and releasing, and the stability of the final product.

The variations are presented in order of increasing stability.

Sheepshank style loop
This version of the knot uses a sheepshank, in this kind of application also known as a bell ringer's knot, to form the loop. It is quicker to make than a fixed loop, but is less dependable. It is avoided in critical applications (such as securing a load on a truck) as it can fall apart under too little load or too much load, and can capsize if not dressed properly. However, this knot may be made secure by adding a Half Hitch to the top bight of the Sheepshank. This form of the trucker's hitch is least likely to jam, coming apart easily once tension is released. Different sources show slight variations in the way the sheepshank portion is formed and dressed.

Versions popular in East Asia use variations of sheep shank using either a simple half hitch or a double turn self crossing half hitch or a triple turn self crossing half hitch. A sheep shank with two consecutive half hitches i.e. a clove hitch to secure the upper eye and to form the lower eye is more popular in the west.

Slipped overhand loop
The loop formed in one version is a simple Slipped Overhand Loop. This version is good for light to moderate loads

Simple friction loop
Another version uses a multiply twisted bight to pass a bight of the working end to form the eye of the loop. This version tolerates higher load.

Fixed loop
The most reliable common variation uses a fixed loop, such as an alpine butterfly loop, artillery loop, figure-eight loop or directional figure-eight loop, or another of many suitable loop knots. If a fixed loop is used repeatedly for tying the trucker's hitch in the same portion of rope, excessive wear or other damage may be suffered by the portion of the loop which working end slides against.

If extra loops are used to form the eye it tends to ease untying. In order to prevent the closing of the loop under load, the loop must be formed by the working end of the rope (which will later pass through the loop). If the standing end goes through the loop, it will close under load.

Finishing the hitch
In tightening the trucker's hitch, tension can be effectively increased by repeatedly pulling sideways while preventing the tail end from slipping through the loop, and then cinching the knot tighter as the sideways force is released. This is called "sweating a line".

If the tail end is wrapped through the last loop twice, the resulting friction may render manual cinching unnecessary.

Once tight, the trucker's hitch is often secured with a half hitch, usually slipped for easy releasing and to avoid the necessity of access to the end of the rope, though a more secure finish, such as two half-hitches, may be called for. Under large loads, the finishing half hitch can jam, especially if it is not slipped; the difficulty of releasing it can be compounded by the fact that the knot is typically still under tension when it is to be untied.

Finishing with a taut-line hitch or a Farrimond friction hitch to the standing part allows the finishing knot to be tied and untied with no tension. This eliminates any jamming problems and also allows the line to be re-tensioned if necessary.

A mechanical advantage of ideally 3:1 can nearly be achieved when using an equivalent setup with pulleys, but is reduced substantially by friction when using knots.

Cultural references
The trucker's hitch knot is portrayed by comedy duo Ylvis in their 2014 song with the same name. The lyrics and the video pretend (in a humorous way) to demonstrate how to tie the knot.

title: Trucker's hitch


text:
Hangman's knot

The hangman's knot or hangman's noose (also known as a collar during the Elizabethan era) is a knot most often associated with its use in hanging a person.

Function
This knot was typically used as a method of capital punishment. The pull on the knot at end of the gallows often resulted in a cervical fracture. Another method intended to result in the mass of the knot crushing closed (occluding) neck arteries, causing cessation of brain circulation, which was not always rapid. The knot is non-jamming but tends to resist attempts to loosen it.

In culture
Surviving nooses in the United Kingdom show simple slipknots that were superseded in the late 19th century with a metal eye spliced into one end of the rope, the noose being formed by passing the other end through it. The classic hangman's knot was largely developed in the United States. Filmed hangings of war criminals in Europe after World War II, conducted under US jurisdiction, show such knots placed in various locations.

Each additional coil adds friction to the knot, which makes the noose harder to pull closed or open. When Grover Cleveland was the sheriff of Erie County, he performed two hangings. Cleveland was advised by a more experienced Sheriff to grease the rope with tallow and run it through the knot a few times to ensure rapid closure with the drop. The number of coils should therefore be adjusted depending on the intended use, the type and thickness of rope, and environmental conditions such as wet or greasy rope. One coil makes it equivalent to the simple running knot.

Woody Guthrie sings of the hangman using thirteen coils:

Did you ever see a hangman tie a hangknot? I've seen it many a time and he winds, he winds, After thirteen times he's got a hangknot.

title: Hangman's knot


text:
Talk:Hangman's knot

Instructions?
''I was about to write this then decided maybe we should not describe here how to tie this. Hmph. --Justfred''

Some would say that's stifling the free interchange of information. But anyway... This article could certainly do with fleshing out. It doesn't stand well on it's own. Darac 21:57, 5 Nov 2003 (UTC)

I also believe there is absolutely no reason to leave out information. My memory tells that there are actually two versions of the knot. One can be pulled open and another one can not. The non-opening version can be pulled tightly shut in order to make a very convenient throwing weight for an end of any rope of suitable thickness. --blades 01:48, May 11, 2004 (UTC)

The article seems to have improved. The thirteen turns sounds like one of those things that people keep adding to myths and stories to make them seem more mystical. Then again, maybe it is something people would really have done to make the event seem more mystical. I am not a hangman, so I can't tell for sure :) --blades 09:42, 30 May 2004 (UTC)

Name change
I believe the correct name for this knot is the "Hangman's knot". A noose is the simplest kind of running knot. - From the Morrow guide to knots. ISBN 0-688-01226-4

thirteen loops
I thought a Hangman's noose traditionally had thirteen loops. Is this not true?

Pud 01:40, 15 Jul 2004 (UTC)

 * Each additional loop adds friction to the knot, so you adjust the number of loops according to how easily you want the knot to slide, and depending on the type and condition of the rope. 7 loops is the normal way of tying this knot (for natural rope), while 13 loops makes the knot look rather ugly (very elongated on most ropes) and a bit more unstable as the knot itself starts to bend.

 * I'll write some more on the main page if nobody minds, as there are "significant non-infringing [to life] uses" of the knot, and lots of history, politics and intregue to write about. Ojw 19:18, 5 Feb 2005 (UTC)

 * From what I've seen (looking at old photos), there actually are 13 loops. It makes sense, as people have always been superstitious. ~ Wakanda's Black Panther! (contribs) 01:02, 30 August 2007 (UTC)

 * Only hearsay I'm afraid but I have heard that it was 13 for a normal man, 15 for a stout one - possibly due to the fact that a lot of pressure can cause the "locking" loop at the top to be pulled through the other loops, runing the knot - Excuse the layman terms Basiclife (talk)

Not dangerous?
User:64.40.45.208 wrote "There is nothing intrinsically dangerous about the hangman's noose itself.". Howabout its tendancy to shut easily and not open? Ojw 19:23, 3 Mar 2005 (UTC)

Depends on which end you are at (g). —Preceding unsigned comment added by 76.191.135.66 (talk) 20:32, 9 December 2009 (UTC)

 * I think, for the sake of pretty much and whatever credibility Wikipedia might have, this article would be better off without a "Tying it" section.

 * It's been discussed as whether or not to give instruction on tying the knot, because it might be dangerous. I really don't see any danger here. If someone's to kill themselves or someone else, they probably won't search Wikipedia. Besides that, instructions on how to tie one would give a good visual on what they look like and how they work/worked. Seems to me the real danger lies in the "just under the left ear" bit, because it "does the job" instantly. This article probably ought to be re-written, with instructions on the knot(or a good picture) added. But that's just my opinion. ~ (Wakandas black panther 06:04, 21 August 2007 (UTC))

 * Unfortunately, I think how to tie it should be listed as I hate the idea of hiding the facts (especially when there are thousands of sites demonstrating the knot available). I would, however, suggest that it may be worth adding some sort of warning/disclaimer tag. Something like : Warning! This knot can tighten easily and should not be used on a human as serious injury/death can result (Ok, it's late and I'm tired but you get the point) Basiclife (talk) —Preceding comment was added at 20:22, 2 April 2008 (UTC)

 * I just came to Wikipedia to look on how to tie this knot and was disappointed that such knowledge is hidden. I am going to hang myself now (I found how to tie knot on: http://www.geocities.com/roo_two/hangmansnoose.html and http://www.metacafe.com/watch/285151/hangmans_knot/), because I don't want to live in a world where knowledge in encyclopedias is filtered... ;( ~ (Hangman 17:40, 25 October 2008 (UTC))  —Preceding unsigned comment added by 77.105.26.103 (talk)

 * I doubt anyone who has had a relative or a friend hang themselves would have made that joke. George 137.111.47.29 (talk) 01:52, 5 December 2008 (UTC)

 * I think how to tie this knot should be included. That's what I came here to find out (to repair a Cleudo piece, of all things).  There seems to be a consensus on this (5 for, 2 against, several people who have commented on this topic but not expressed a definite view either way on this talk page), and there's already a picture that tries to show it, so pretty soon I'm going to add it in text.

 * Incidentally, I have edited the comments in this section just to properly indent them. Previously it looked like Wakandas black panther also wrote the comment above theirs, and hence they appeared to change their mind in mid-comment. Lessthanideal (talk) 16:40, 29 January 2009 (UTC)

The fact is, most every boy knows how to tie this knot. When I went through Army training, in the rope practice sections the instructor warned us. "When getting your bowlines ready for inspection, I don't want to see any examples of 'The Hangman's Knot'. We are here to test all knots made, so maybe we'll test that one!" They were kidding, of course. I'm pretty sure. But the point is, they had obviously run into it before, thus the warning.

As it happened, I learned it in the fith grade; it was not part of the school curriculum, tho (g). Some bits of knowledge just have inherent interest. So, I vote against a ban; it is not liable to lead to a rash of hangings and Wiki would be shutting the stable door, anyway. 76.191.135.66 (talk) 20:31, 9 December 2009 (UTC)

User:ojw wrote: "Howabout its tendancy to shut easily and not open?". The hangman's knot doesn't have any "ratchet" effect; if it's tightened enough to be hard to open it will be quite hard to close as well. Rabbitflyer (talk) 17:33, 27 June 2020 (UTC)

Other uses
I added a section on other uses. Basically a "hangman's knot" is the same as fishing's uni knot. I was going to give directions on tying it on the uni knot page, but wondered if maybe I should remove the other uses section that I put in with the link to the uni knot page for all the reasons listed above.
 * Isn't it so that when you tie a uni knot and pull it tight you get:
 * Loose end - straight - winding - straight - loop - straight - main rope
 * Whereas the hangman's knot goes like:
 * Loose end - winding - straight - straight - loop - straight - main rope
 * So I don't think they're quite identical. 82.139.87.182 (talk) 20:34, 4 October 2009 (UTC)

History
Is there a reason why the line "this knot was offten used to kil slaves and people that were accused of being a witch. They would have the knot around your neck and make you stand on a deck then they would push you off causing the tightness of the rope to beak your neck" is there? It seems rather pointless as a) the spelling is poor, b) its pointing out a specific use when the actual use was more general (i.e. not just slaves and witches, also used from horse back), and c) it's preceded by the line "The Hangman's Knot was used on ropes in Colonial America as well as England during the 17th and 18th centuries as a way to execute condemned people easily. The knot would break a person's neck if tied correctly, otherwise the person was simply left to strangle to death."

If there is feel free to revert it, otherwise I removed this bit of repitition. 01:55, 25 April 2006 (UTC)

Copyright?
Most text is directly copied and the rest just a re-written version of http://www.geocities.com/roo_two/hangmansnoose.html

Rope length
Is their not a formula to calculate the length of the rope considering the weight of the person? I think this is relevant information that should be added.

Yes, there is. But it's not relevant to the knot, only to the practice of hanging which is where it's referenced. RedHillian 00:16, 30 December 2006 (UTC)

striking force
additional striking force to the back of the neck? is that even significant? seems like it needs a citation Cannibalicious!

A couple of Comments
JayMill 04:27, 6 October 2007 (UTC)The neck-breaking force is due to the twisting motion. Noose's are never placed directly behind the neck, always off to the side, so as you drop, it swivels, placing pressure transversely on the cervical vertebrae. The C-section of the spine twists, severing the spinal column. Thus, death. I was always told it was tied with 13 knots, however in practice, its nearly impossible to do so with a thinker rope. What bothers me is the title. The hangman's knot was typically used for strangulation hangings, where the noose was used for dead-drop hangings. I just wanted to add that, it's your call.

 * Isn't it ideally placed in front, swiveling to the left side upon drop? I believe that info comes from Geo Stone's book.  And what's the source for claiming that the hangman's knot was for strangulation hangings?!?  68.83.72.162 (talk) 14:38, 10 May 2009 (UTC)

AKA parade knot
The knot is also known as a “parade knot”. It was used by the US Calvary (and other horse units) when they were leading their horses while in foot. The intent of this parade knot was to serve as a way to humanely maintain control of a horse during a parade where it could be suddenly startled.

The loop of the noose was tightened around the muzzle of the horse. The lead, along with the reins, were held in the off hand and the coils were held in the hand closest to the horse. If the horse started to skitter, the person leading the horse could take the coils and cant them against the horses jaw. This would cause the loop to temporally tighten but would loosen when the coils were moved to the original perpendicular position. This technique was used to provide temporary control over an otherwise well disciplined horse.

What I would like to see in this article (and I will start doing some research) is what are the different “knots” used for judicial hangings? I know that the British used a spliced running loop lined with chamois leather. I also believe that US military hangings used a similar spliced running noose. It would be interesting to find out whether other countries used the “hangman’s/parade knot”. It would also be interesting to find out when the hangman’s/parade knot was first used for judicial hangings in this country and how it was chosen.

One theory I have read indicated that the bulk of the coils of the hangman’s/parade knot would impact the mastoid process of the condemned, knocking them out. I don’t know whether this theory is accurate or not. Throckmorton Guildersleeve (talk) 17:07, 24 December 2007 (UTC)

What about political implications or symbolism?
If I hung a rope from a tree in the middle of town square with a bow tie at the end, it would be ignored until park employees removed it. However if that rope ended in a Hangman's Noose, it would make news headlines that very evening. The act alone could possibly even be considered a "Hate Crime". Of all the knots you can tie, this is the only one that invokes fear and anger in people and even carries connotations of racism. Also people have been penalized and even fired from their jobs over this particular knot... even just for DRAWING a picture of one! So I believe this topic is notable enough to be included in this article. If a rope was found in a tree in the front yard of Barack Obama, that was tied in a Hangman's Noose, it would be the top story of every media outlet on earth. BillyTFried (talk) 15:40, 21 June 2008 (UTC)

Man gets 4 months for threatening 'Jena 6' protesters with noose

http://www.cnn.com/2008/CRIME/08/15/jena.noose/
 * Jeremiah Munsen, 19, pleaded guilty to federal hate crime charges in April
 * Munsen admitted driving past protesters with noose dangling from truck
 * Protesters were waiting at bus depot after rally in Jena 6 case
 * Rally concerned criminal charges for six black teens in attack on white teen

BillyTFried (talk) 20:20, 18 August 2008 (UTC)

Hangman's knot in racism
I made an edit to the hangman's noose page today. It's really poorly written though so talented writers and wiki editors may want to go in and fix it. Thanks. Djclimber (talk) 21:29, 15 December 2008 (UTC)

Post script
BillyTFried is onto some good points. It is definitely worth noting that it would be really idiotic to display this knot where it could be publicly viewed. I wrote a snippet on that but something more detailed--and with citations--should be posted. Thanks! 69.134.178.168 (talk) 07:56, 16 December 2008 (UTC)

History section is poor
All the History section says is "The hangman's knot was used on ropes in Colonial America as well as England during the 16th and 18th centuries.". Immediately two questions spring to mind

 * 1) What did they do in the 17th century?
 * 2) The hanging article says in England it was used for judicial punishment from around 400 to 1964.  Did they use other knots in that period?

Maybe they used other types of knot - I'm no expert. Needs to be clarified though. The hanging article seems quite extensive, so maybe just put a link in to that for execution information if this knot was used in most cases.

This article should say when and where the knot originated, and its history (if any) outside executions. Lessthanideal (talk) 16:25, 29 January 2009 (UTC)

 * Any kind of noose will kill if one is suspended by the neck, whether the neck is broken or not. Historically, death by hanging meant strangulation, not a quick end due to cervical fracture as executions were not meant to be painless or quick.  There is a lot of entertainment value in watching someone struggling at the end of a noose.  A much earlier knot used was the scaffold knot (http://www.expertvillage.com/video/73193_knot-tying-tips-multiple-scaffold.htm), which also is a self locking knot.  I believe this was used extensively in England and elsewhere in Europe until relatively recently.   Several variations on this theme were used at various times and in various jurisdictions.  The hangman's knot became "popular in England during the 17th or 18th century because it was very strong and would not release no matter how hard the victim struggled.  After introduction of the measured drop in late 19th century England a simple loop noose (http://www.capitalpunishmentuk.org/berryn.jpg) was used as a drop of 6 or 7 feet would almost always result in a broken or dislocated neck (if not the victim would still die in a few minutes, albeit more slowly).  In any event, there is very little in the way of struggle when someone is hanged this way.  I am not sure of the dates or many of the particulars of these events but someone could do some serious research on this and greatly improve the article.  The following article gives a very good history of hanging in the UK but little detail is provided about the kind of noose used prior to the 1890s (http://www.capitalpunishmentuk.org/hanging1.html#pinion).  —Preceding unsigned comment added by 139.78.86.166 (talk) 16:54, 22 April 2009 (UTC)

How the Hangman's Noose Kills
There are a number of misconceptions here about how the hangman’s noose kills. To assure a dislocation or fracture of the cervical vertebra a drop of 5 to 7 feet is required (or more especially if the victim is a small woman or child). Tables are available to calculate the drop depending on the weight of the victim (http://www.capitalpunishmentuk.org/hanging2.html). Unconsciousness is almost immediate (supposedly) and death occurred a few minutes later. The “blow” provided by the knot upon a drop of several feet likely ads nothing the process. In fact a simple loop noose was used instead of the hangman’s noose in the U.K. and many other jurisdictions because it was just as effective at causing a neck fracture, especially when the knot is placed toward the front of the neck, and easier to remove when the hanging was over. So the use of the hangman’s noose in modern judicial hangings serves no purpose other than tradition.

Prior to the mid 19th century most hangings were performed with little or no drop off a ladder or the back of a cart and the neck was almost never broken. (This is still the way hangings are carried out in some parts of the world and how most suicide hangings take place.) In such cases it can take 1 to 3 minutes before the victim looses consciousness and he/she may struggle violently during the painful process. The pain largely is due to damage to soft neck tissues caused by the entire body weight being supported by the neck and jaw. Also the victim will feel panic at being unable to breath. Unconsciousness and eventually death results from asphyxia caused by blockage of blood to the brain and not due to lack of air in the lungs. Note, in some cases death may occur very quickly after suspension due to heart stoppage caused by the vagal reflex. This is why it is extremely dangerous to play at hanging even if the victim is suspended only for a few seconds.

In the case of a short drop or suspension hanging there is an advantage to a self-locking knot like the hangman’s knot. If properly tied and lubricated with wax or soap it will tighten under the weight of the victim but will not loosen during the inevitable struggle, accomplishing the strangulation process more rapidly. Also, the tradition of placing the knot below the ear has the advantage of obstructing both the carotid and vertebral arteries resulting in more rapid unconsciousness. In fact, condemned prisoners were known to request bribe hangmen to properly place the noose at the side of the neck before being executed. —Preceding unsigned comment added by 74.195.236.222 (talk) 17:50, 12 April 2009 (UTC)
 * I also don't understand how a knot could provide an extra blow. Maybe a particular shape of knot could keep the head in a position that makes the drop more effective, but adding an extra blow? That seems very implausible to me, I'll remove it from the article. 82.139.87.182 (talk) 20:43, 4 October 2009 (UTC)

Adding my two cents of knowledge on the subject. First, the size of the knot does play a role in the power of the action induced in a hanging. The size of the rope is almost as important as the number of knots, or rolls used in creating the knot. It is basically the different between being hit by a 16oz boxing glove, and a 9oz. The knot serves as a cantilever point, bigger is better. The goal of a proper hanging, is the severing of the spine between C1 vertebra, and C2. This is above the nerves that branch off of the neck vertebra and control reflexive breathing, therefore breathing ceases immediately. As an example, everyone has seen a quadriplegic that has lost all ability to control their body, yet they still breathe. This is because in the grand design of the body, the nerves that control reflexive breathing, are placed at the highest point of the neck, protecting it from common fractures, the knot and proper drop remove this factor and cause death much more rapidly.

Another aspect of the hanging game, one which you will remember and share with your friends, is the term "well hung". Most people do not know the etymology of the phrase, and believe it has to do with the size of the male organ, this is false. The term well hung, comes from the 1800's, possibly earlier. When a person is hung properly, the breaking of the spinal cord between C1 and C2 causes a condition know as priapism in men. That is to say, they get an erections, even in death. When a man was hung from the gallows, a doctor would check the condemned by pulling open his pants, if the condemned had an erection, the doctor would proclaim that he was indeed "well hung".

From what I learned in my time as a medic, this type of injury to the spinal cord causes instant death, basically detaching the spinal cord and damaging the brainstem itself, which is the core basic function center, once those lights go out, it's basically over. There are two forms of death, clinical and biological. Clinical is when the brain ceases to function on any level that we recognize as life itself, no awareness, pain, thoughts, dreams, everything that makes us alive, ceases. One can be clinically dead, but still have function in their body, these are the people on life support, but they are actually gone already. Biological death occurs once the heart stops beating and the organs fail, which begins to occur the moment oxygen is no longer feeding the cells. Some parts die faster than others, which is why preserving the organs for transplant must be done as rapidly after biological death as possible.

Hope this added info informs and entertains, stalker6recon — Preceding unsigned comment added by 112.207.214.249 (talk) 14:37, 13 September 2016 (UTC)

Illustration Needed
The current alleged illustration consists of an off-white rectangle, being slightly impinged upon the right border by what appears to be a much smaller blue rectangle. Nothing else is visible -- rope, noose, knot -- nothing. How about an actual illustration of the knot? — Preceding unsigned comment added by 74.95.43.249 (talk) 03:13, 7 March 2017 (UTC)

Need more detailed description of how the Hangman's knot works.
A more detailed description of how to make the noose is needed. And also scientifically, how does the noose kill ? Is it death by suffocation or breaking one's neck ? Is it a slow painful death or a sudden rapid death ? Aceus0shrifter (talk) 13:57, 16 March 2019 (UTC)
 * it all really depends, if you do it the wrong way. (jumping off something too low) you will suffocate a slow painful death and if you do it the right way (jumping off something high enough to snap your neck). you will have a quick painless death. MapleShade Of The Dark Forest (talk) 19:57, 9 June 2019 (UTC)
 * All that stuff is explained in depth in the Hanging article. This article is limited to describing the knot and some uses for it.  21:58, 9 June 2019 (UTC)

Should this contain the suicide sidebar?
and maybe a disclaimer box thingy like in WP:SOS? Sanchopancho02 (talk) 04:48, 23 July 2023 (UTC)
 * I don't think so; the focus of this article is quite removed from suicide; takes the reader to Suicide by hanging before they encounter an established Suicide sidebar. It's only one possible way this knot might be employed.   14:13, 24 July 2023 (UTC)

Removal of Gif in Infobox
Many users have repeatedly removed the gif found in the infobox due to the it being perceived as dangerous. I also find the gif problematic because of the serious danger for someone to use it for the purpose of self harm or suicide. I am aware that Wikipedia is not considered censored, however, it is also Wikipedia policy that images should not be offensive unless there is serious encyclopedic value in its inclusion. There are other images of the hangman's knot that do not show how to tie it, such as the image already included in the page. I want to seek consensus on removing the gif in the page, and if the consensus desires an image to replace it with, it ought to be one that does not show others how to tie this knot.

Note: I'm still a novice at editing, so if there is anything else that needs to be included to formally request this change, such as tagging an administrator, I ask that a more informed Wikipedia editor make the proper additions. Thanks!

Roccoharde (talk) 22:31, 24 February 2024 (UTC)
 * Please read WP:NOTCENSORED, which is a Wikipedia policy. A simple gif showing how the knot is constructed is highly relevant to the subject. You've already found an administrator, but you don't need a one "formally request a change." You need to establish a policy-based consensus from established users. OhNo itsJamie Talk 22:53, 24 February 2024 (UTC)
 * It cannot be reasonably argued that an image showing how a knot is formed is offensive or dangerous. If you really want a silly discussion, I put it to you that someone wishing to engage in hanging is likely to cause more offence and be more dangerous without clear instructions. I however don't think a silly discussion is at all helpful. The article is about a knot. It should include description of its form and function. Images are encouraged in all articles. The image is a visual description of how the knot is formed. There is no reason to remove the image. All the recent edits appear to be nothing more than an effort to sanitise the article in accordance with some agenda, all under the guise of cleaning up with minor edits. Trying in every way to hide the truth is contrary to the fundamental principals of Wikipedia.  17:59, 25 February 2024 (UTC)

title: Talk:Hangman's knot


text:
Thief knot

The thief knot resembles the reef knot (square knot) except that the free, or bitter ends are on opposite sides. It is said that sailors would secure their belongings in a ditty bag using the thief knot, often with the ends hidden. If another sailor went through the bag, the odds were high the thief would tie the bag back using the more common reef knot, revealing the tampering, hence the name. It is difficult to tie by mistake, unlike the granny knot, unless one attempts to tie a square knot in a similar manner to a sheet bend (which is the correct way to tie a thief knot), then it is possible to tie accidentally.

The thief knot is much less secure than the already insecure reef knot. It unties itself if the lines are pulled when the same action would seize a reef knot.

"The thief or bag knot is also called bread bag knot. It appears very like the reef knot, but there is one real and scarcely evident difference. It does not consist of two half knots. There is a legend that sailors tie clothesbags, and bread bags with this knot and that thieves always retie them with reef knots and so are inevitably detected. It is a pleasing story that should encourage honesty. However, if I have ever met this knot in practical use, I have neither recognized it nor paid penalty for my failure to do so."

- The Ashley Book of Knots

title: Thief knot