It has been suggested that Peak Inverse Voltage be merged into this article or section. (Discuss)

Closeup of the image below, showing the square shaped semiconductor crystal

various semiconductor diodes, below a bridge rectifier

Structure of a vacuum tube diode

In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge carriers through it (this directionality is sometimes generically called the rectifying property). The most common function of a diode is to allow an electric current to flow in one direction (called the forward biased condition) but to block it in the opposite direction (the reverse biased condition). Thus, the diode can be thought of as an electronic version of a check valve. Real diodes do not display such a perfect on-off directionality but usually have complicated and non-linear electrical characteristics, which depend on the particular type of diode technology. Diodes also have many other functions in which they are not designed to operate in this on-off manner. Image File history File links Mergefrom. ... It has been suggested that this article or section be merged into Diode. ... Image File history File links Download high-resolution version (1735x1280, 580 KB) Close-up view of a silicon diode. ... Image File history File links Download high-resolution version (1735x1280, 580 KB) Close-up view of a silicon diode. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A diode bridge is an electronic circuit that provides the same polarity of output voltage and current for both possible polarities of input power. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... This article is about the engineering discipline. ... Objects used in tandem with electricity. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... Electric current is the flow (movement) of electric charge. ... this siamese clappered inlet allows one or two inputs into a deluge gun A check valve is a mechanical device, a valve, that normally allows fluid or gas to flow through it in only one direction. ... To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ...

Early diodes included “cat’s whisker” crystals and vacuum tube devices (called thermionic valves in British English). Today the most common diodes are made from semiconductor materials such as silicon or germanium. A Cats Whisker is the tiny wire that connects to the detector in a crystal radio. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ... British English (BrE, BE, en-GB) is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere in the Anglophone world. ... A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... Not to be confused with Silicone. ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Standard atomic weight 72. ...

History

Thermionic and solid state diodes developed in parallel. The principle of operation of thermionic diodes was discovered by Frederick Guthrie in 1873.^[1] The principle of operation of crystal diodes was discovered in 1874 by the German scientist, Karl Ferdinand Braun.^[2] Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... Frederick Guthrie was a scientific writer and professor in London who lived from 1833 to 1886. ... Karl Ferdinand Braun (6 June 1850 in Fulda, Germany – 20 April 1918 in New York City, USA) was a German inventor, physicist and Nobel Prize laureate. ...

Thermionic diode principles were rediscovered by Thomas Edison on February 13, 1880 and he was awarded a patent in 1883 (U.S. Patent 307,031 ), but developed the idea no further. Braun patented the crystal rectifier in 1899 [1]. Braun’s discovery was further developed by Sir Jagdish Bose into a useful device for radio detection. “Edison” redirects here. ... is the 44th day of the year in the Gregorian calendar. ... Year 1880 (MDCCCLXXX) was a leap year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Tuesday of the 12-day slower Julian calendar). ... Year 1883 (MDCCCLXXXIII) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day slower Julian calendar). ... Sir Jagadish Chandra Bose (Bengali: Jôgdish Chôndro Boshu) (November 30, 1858 – November 23, 1937) was a Bengali physicist from undivided India, who pioneered the investigation of radio and microwave optics and made extremely significant contributions to plant science. ...

The first radio receiver using a crystal diode was built around 1900 by Greenleaf Whittier Pickard. The first thermionic diode was patented in Britain by John Ambrose Fleming (scientific adviser to the Marconi Company and former Edison employee[2]) on November 16, 1904 (U.S. Patent 803,684  in November 1905). Pickard received a patent for a silicon crystal detector on November 20, 1906 [3] (U.S. Patent 836,531 ). Äž: For the film, see: 1900 (film). ... Greenleaf Whittier Pickard (February 14, 1877, Portland, Maine - January 8, 1956, Newton, Massachusetts) was a United States radio pioneer. ... Sir John Ambrose Fleming (November 29, 1849 - April 18, 1945) was an English electrical engineer and physicist. ... The Marconi Company Ltd. ... is the 320th day of the year (321st in leap years) in the Gregorian calendar. ... 1904 (MCMIV) was a leap year starting on a Friday (see link for calendar). ... is the 324th day of the year (325th in leap years) in the Gregorian calendar. ... 1906 (MCMVI) was a common year starting on Monday (see link for calendar). ...

At the time of their invention such devices were known as rectifiers. In 1919 William Henry Eccles coined the term diode from Greek roots; di means ‘two’, and ode (from odos) means ‘path’. A rectifier is one or more diodes arranged for converting alternating current (AC) to direct current (DC). ... Year 1919 (MCMXIX) was a common year starting on Wednesday (link will display the full calendar). ... Physicist William Eccles William Henry Eccles (August 23, 1875 - April 29, 1966) was a British physicist and a pioneer in the development of radio communication. ... The following is an alphabetical list of Greek and Latin roots commonly used in English uced in Medicine and Medical Terminology are not listed here but instead in Wikipedias List of medical roots. ...

Thermionic or gaseous state diodes

The symbol for an indirect heated vacuum tube diode. From top to bottom, the components are the anode, the cathode, and the heater filament.

Thermionic diodes are thermionic valve devices (also known as vacuum tubes), which are arrangements of electrodes surrounded by a vacuum within a glass envelope, similar in appearance to incandescent light bulbs. Image File history File links Vacuum_diode. ... Image File history File links Vacuum_diode. ... In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... For other uses, see Electrode (disambiguation). ... Light bulb redirects here. ...

In thermionic valve diodes, a current is passed through the heater filament. This indirectly heats the cathode, another filament treated with a mixture of barium and strontium oxides, which are oxides of alkaline earth metals; these substances are chosen because they have a small work function. (Some valves use direct heating, in which the heating current is passed through the cathode itself.) The heat causes thermionic emission of electrons into the vacuum envelope. In forward operation, a surrounding metal electrode, called the anode, is positively charged, so that it electrostatically attracts the emitted electrons. However, electrons are not easily released from the unheated anode surface when the voltage polarity is reversed and hence any reverse flow is a very tiny current. An electrical filament is a thread of metal, usually tungsten, which is used to convert electricity into light in incandescent light bulbs (as developed in 1878 by Joseph Wilson Swan, among others), and into heat in vacuum tube devices. ... Diagram of a copper cathode in a Daniells cell. ... For other uses, see Barium (disambiguation). ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Standard atomic weight 87. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). ... The work function is the minimum energy (usually measured in electron volts) needed to remove an electron from a solid to a point immediately outside the solid surface. ... Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... Diagram of a zinc anode in a galvanic cell. ... Electrostatics (also known as static electricity) is the branch of physics that deals with the phenomena arising from what seem to be stationary electric charges. ...

For much of the 20th century thermionic valve diodes were used in analog signal applications, and as rectifiers in power supplies. Today, valve diodes are only used in niche applications, such as rectifiers in guitar and hi-fi valve amplifiers, and specialized high-voltage equipment.

Semiconductor diodes

Most modern diodes are based on semiconductor p-n junctions. In a p-n diode, conventional current can flow from the p-type side (the anode) to the n-type side (the cathode), but cannot flow in the opposite direction. Another type of semiconductor diode, the Schottky diode, is formed from the contact between a metal and a semiconductor rather than by a p-n junction. A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Diagram of a zinc anode in a galvanic cell. ... Diagram of a copper cathode in a Daniells cell. ... Schottky diode schematic symbol The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action. ...

A semiconductor diode’s current-voltage, or I-V, characteristic curve is related to the transport of carriers through the so-called depletion layer or depletion region that exists at the p-n junction between differing semiconductors. When a p-n junction is first created, conduction band (mobile) electrons from the N-doped region diffuse into the P-doped region where there is a large population of holes (places for electrons in which no electron is present) with which the electrons “recombine”. When a mobile electron recombines with a hole, both hole and electron vanish, leaving behind an immobile positively charged donor on the N-side and negatively charged acceptor on the P-side. The region around the p-n junction becomes depleted of charge carriers and thus behaves as an insulator. A current-voltage characteristic is a chart showing the relationship between the DC current through an electronic device and the DC voltage across its terminals. ... In semiconductor physics, the Depletion Zone or Depletion layer is a nonconductive region within a conductive, doped semiconductor material where the charge carriers have been swept away. ... In semiconductor physics, the depletion region, also called depletion layer or depletion zone, is an insulating region within a conductive, doped semiconductor material where the charge carriers have been swept away through recombination. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... Nonconductors or electrical insulators are materials which lack movable electric charges, and which therefore lack a low-resistance path for charge flow. ...

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

If an external voltage is placed across the diode with the same polarity as the built-in potential, the depletion zone continues to act as an insulator preventing a significant electric current. This is the reverse bias phenomenon. However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed resulting in substantial electric current through the p-n junction. For silicon diodes, the built-in potential is approximately 0.6 V. Thus, if an external current is passed through the diode, about 0.6 V will be developed across the diode such that the P-doped region is positive with respect to the N-doped region and the diode is said to be “turned on” as it has a forward bias. A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...

I-V characteristics of a P-N junction diode (not to scale).

A diode’s I-V characteristic can be approximated by four regions of operation (see the figure at right). Image File history File links Rectifier_vi_curve. ...

At very large reverse bias, beyond the peak inverse voltage or PIV, a process called reverse breakdown occurs which causes a large increase in current that usually damages the device permanently. The avalanche diode is deliberately designed for use in the avalanche region. In the Zener diode, the concept of PIV is not applicable. A Zener diode contains a heavily doped p-n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material, such that the reverse voltage is “clamped” to a known value (called the Zener voltage), and avalanche does not occur. Both devices, however, do have a limit to the maximum current and power in the clamped reverse voltage region.

The second region, at reverse biases more positive than the PIV, only a very small reverse saturation current flows. In the reverse bias region for a normal P-N rectifier diode, the current through the device is very low (in the µA range).

The third region is forward but small bias, where only a small forward current is conducted.

Finally, as the potential difference is increased above a cut-in voltage or on-voltage, the diode current becomes appreciable (the level of current considered "appreciable" and the value of cut-in voltage depends on the application), at which point it can be thought of as a connection with zero (or at least very low) resistance. More precisely, the current-voltage curve is exponential, and is so sharp that it looks like a corner on a zoomed-out graph (see also signal processing). In a normal silicon diode at rated currents, the cut-in voltage is approximately 0.6 to 0.7 volts. The value is different for other diode types — Schottky diodes can be as low as 0.2 V and light-emitting diodes (LEDs) can be 1.4 V or more (Blue LEDs can be up to 4.0 V).

It has been suggested that this article or section be merged into Diode. ... Avalanche breakdown is a phenomenon that can occur in both insulating and semiconducting materials. ... An avalanche diode is a diode (usually made from silicon, but can be made from another semiconductor) that is designed to break down and conduct at a specified reverse bias voltage. ... Zener diode schematic symbol A Zener diode is a type of diode that permits current to flow in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger (not equal to, but larger) than the rated breakdown voltage known as Zener knee... Signal processing is the processing, amplification and interpretation of signals, and deals with the analysis and manipulation of signals. ... Josephson junction array chip developed by NIST as a standard volt. ... Schottky diode schematic symbol The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action. ... “LED” redirects here. ...

Shockley diode equation

The Shockley ideal diode equation or the diode law (named after transistor co-inventor William Bradford Shockley, not to be confused with tetrode inventor Walter H. Schottky) is the I-V characteristic of an ideal diode in either forward or reverse bias (or no bias). It is derived with the assumption that the only processes giving rise to current in the diode are drift (due to electrical field), diffusion, and thermal recombination-generation. It also assumes that the recombination-generation (R-G) current in the depletion region is insignificant. This means that the Shockley equation doesn’t account for the processes involved in reverse breakdown and photon-assisted R-G. Additionally, it doesn’t describe the “leveling off” of the I-V curve at high forward bias due to internal resistance, nor does it explain the practical deviation from the ideal at very low forward bias due to R-G current in the depletion region. Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... William Bradford Shockley (February 13, 1910 – August 12, 1989) was a British-born American physicist and inventor. ... This article does not cite any references or sources. ... Walter H. Schottky (July 23, 1886, Zürich, Switzerland - March 4, 1976, Pretzfeld, West Germany) was a German physicist who invented the screen-grid vacuum tube in 1915 and the tetrode in 1919 while working at Siemens. ...

where

I is the diode current,

I_S is a scale factor called the saturation current,

V_D is the voltage across the diode,

V_T is the thermal voltage,

and n is the emission coefficient, also known as the ideality factor.

The thermal voltage V_T is approximately 25.85 mV at 300 K, a temperature close to "room temperature" commonly used in device simulation software. At any temperature it is a known constant defined by: Ludwig Boltzmann The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ... Emission coefficient is a coefficient in the power output per unit time of an electromagnetic source, a calculated value in physics. ... Ludwig Boltzmann The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ...

where

q is the magnitude of charge on an electron (the elementary charge),

k is Boltzmann's constant,

T is the absolute temperature of the p-n junction in Kelvins

For even rather small voltages the exponential is very large because the thermal voltage is very small, so the subtracted "1" in the diode equation is negligible and the diode current is often approximated as For other uses, see Electron (disambiguation). ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ... For other uses, see Kelvin (disambiguation). ...

The emission coefficient n varies from about 1 to 2 depending on the fabrication process and semiconductor material and in many cases is assumed to be approximately equal to 1 (thus the notation n is omitted).

The use of the diode equation in circuit problems is illustrated in the article on diode modeling. To meet Wikipedias quality standards, this article or section may require cleanup. ...

Hydrodynamic analogy

Main article: Hydraulic analogy

The diode, in the manner of a valve, allows the passage of the current only in one direction. It is a polarized dipole, the anode and cathode is thus located on the component. Since electric current is invisible and the processes at play in electronics are often difficult to understand in an intuitive way, it is common to teach electronics using analogies to more common sense objects and processes. ...

The valve is closed, the current is blocked Image File history File links No higher resolution available. ...	The valve is opened, the current passes Image File history File links No higher resolution available. ...

Types of semiconductor diode

Diode	Zener Diode	Schottky Diode	Tunnel Diode
Light-emitting diode	Photodiode	Varicap	SCR

Some diode symbols

There are several types of junction diodes, which either emphasizes a different physical aspects of a diode often by geometric scaling, doping level, choosing the right electrodes, are just an application of a diode in a special circuit, or are really different devices like the Gunn and laser diode and the JFET: Image File history File links Diode_symbol. ... Image File history File links Zener_diode_symbol. ... Image File history File links Schottky_diode_symbol. ... Image File history File links Tunnel_diode_symbol. ... Zener diode schematic symbol A Zener diode is a type of diode that permits current to flow in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger (not equal to, but larger) than the rated breakdown voltage known as Zener knee... Schottky diode schematic symbol The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action. ... Tunnel diode schematic symbol A tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave region GHz, by utilizing quantum mechanical effects. ... Image File history File links LED_symbol. ... Image File history File links Photodiode_symbol. ... Image File history File links Varicap_symbol. ... Image File history File links SCR_symbol. ... “LED” redirects here. ... Photodiode closeup A photodiode A photodiode is a semiconductor diode that functions as a photodetector. ... Varicap schematic symbol A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ... A Silicon Controlled Rectifier (or semiconductor controlled rectifier) is a 4-layer solid state device that controls current flow. ...

Normal (p-n) diodes

which operate as described above. Usually made of doped silicon or, more rarely, germanium. Before the development of modern silicon power rectifier diodes, cuprous oxide and later selenium was used; its low efficiency gave it a much higher forward voltage drop (typically 1.4–1.7 V per “cell”, with multiple cells stacked to increase the peak inverse voltage rating in high voltage rectifiers), and required a large heat sink (often an extension of the diode’s metal substrate), much larger than a silicon diode of the same current ratings would require. The vast majority of all diodes are the p-n diodes found in CMOS integrated circuits, which include 2 diodes per pin and many other internal diodes.

Switching diodes

Switching diodes, sometimes also called small signal diodes, are a single p-n diode in a discrete package. A switching diode provides essentially the same function as a switch. Below the specified applied voltage it has high resistance similar to an open switch, while above that voltage it suddenly changes to the low resistance of a closed switch. They are used in devices such as ring modulation.

Schottky diodes

Schottky diodes are constructed from a metal to semiconductor contact. They have a lower forward voltage drop than any p-n junction diode. Their forward voltage drop at forward currents of about 1 mA is in the range 0.15 V to 0.45 V, which makes them useful in voltage clamping applications and prevention of transistor saturation. They can also be used as low loss rectifiers although their reverse leakage current is generally much higher than non Schottky rectifiers. Schottky diodes are majority carrier devices and so do not suffer from minority carrier storage problems that slow down most normal diodes — so they have a faster “reverse recovery” than any p-n junction diode. They also tend to have much lower junction capacitance than PN diodes and this contributes towards their high switching speed and their suitability in high speed circuits and RF devices such as switched-mode power supply, mixers and detectors.

Super Barrier Diodes

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

“Gold-doped” diodes

As a dopant, gold (or platinum) acts as recombination centers, which help a fast recombination of minority carriers. This allows the diode to operate at signal frequencies, at the expense of a higher forward voltage drop. Gold doped diodes are faster than other p-n diodes (but not as fast as Schottky diodes). They also have less reverse-current leakage than Schottky diodes (but not as good as other p-n diodes).[4].^[3] A typical example is the 1N914.

Snap-off or Step recovery diodes

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

Point-contact diodes

These work the same as the junction semiconductor diodes described above, but its construction is simpler. A block of n-type semiconductor is built, and a conducting sharp-point contact made with some group-3 metal is placed in contact with the semiconductor. Some metal migrates into the semiconductor to make a small region of p-type semiconductor near the contact. The long-popular 1N34 germanium version is still used in radio receivers as a detector and occasionally in specialized analog electronics.

Cat’s whisker or crystal diodes

These are a type of point contact diode. The cat’s whisker diode consists of a thin or sharpened metal wire pressed against a semiconducting crystal, typically galena or a piece of coal.[5] The wire forms the anode and the crystal forms the cathode. Cat’s whisker diodes were also called crystal diodes and found application in crystal radio receivers. Cat’s whisker diodes are obsolete.

PIN diodes

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

Varicap or varactor diodes

These are used as voltage-controlled capacitors. These are important in PLL (phase-locked loop) and FLL (frequency-locked loop) circuits, allowing tuning circuits, such as those in television receivers, to lock quickly, replacing older designs that took a long time to warm up and lock. A PLL is faster than a FLL, but prone to integer harmonic locking (if one attempts to lock to a broadband signal). They also enabled tunable oscillators in early discrete tuning of radios, where a cheap and stable, but fixed-frequency, crystal oscillator provided the reference frequency for a voltage-controlled oscillator.

Zener diodes

Diodes that can be made to conduct backwards. This effect, called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. In practical voltage reference circuits Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient to near zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes (see below). Two (equivalent) Zeners in series and in reverse order, in the same package, constitute a transient absorber (or Transorb, a registered trademark). They are named for Dr. Clarence Melvin Zener of Southern Illinois University, inventor of the device.

Avalanche diodes

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

Transient voltage suppression diode (TVS)

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

Photodiodes

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

Light-emitting diodes (LEDs)

In a diode formed from a direct band-gap semiconductor, such as gallium arsenide, carriers that cross the junction emit photons when they recombine with the majority carrier on the other side. Depending on the material, wavelengths (or colors) from the infrared to the near ultraviolet may be produced. The forward potential of these diodes depends on the wavelength of the emitted photons: 1.2 V corresponds to red, 2.4 to violet. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time. All LEDs are monochromatic; “white” LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow scintillator coating. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an opto-isolator.

Laser diodes

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

Esaki or tunnel diodes

these have a region of operation showing negative resistance caused by quantum tunneling, thus allowing amplification of signals and very simple bistable circuits. These diodes are also the type most resistant to nuclear radiation.

Gunn diodes

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

Peltier diodes

are used as sensors, heat engines for thermoelectric cooling. Charge carriers absorb and emit their band gap energies as heat.

Current-limiting field-effect diodes

These are actually a JFET with the gate shorted to the source, and function like a two-terminal current-limiting analog to the Zener diode; they allow a current through them to rise to a certain value, and then level off at a specific value. Also called CLDs, constant-current diodes, diode-connected transistors, or current-regulating diodes.[6], [7]

Other uses for semiconductor diodes include sensing temperature, and computing analog logarithms (see Operational amplifier applications#Logarithmic). Not to be confused with Silicone. ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Standard atomic weight 72. ... Copper(I) oxide or cuprous oxide (Cu2O) is an oxide of copper. ... For other uses, see Selenium (disambiguation). ... For other uses, see CMOS (disambiguation). ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... Ring modulation is an audio effect performed by multiplying two audio signals, where one is typically a sine-wave or another simple waveform. ... Schottky diode schematic symbol The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action. ... Walter H. Schottky (July 23, 1886, Zürich, Switzerland - March 4, 1976, Pretzfeld, West Germany) was a German physicist who invented the screen-grid vacuum tube in 1915 and the tetrode in 1919 while working at Siemens. ... A clamper is an electric circuit that prevents a signal from exceeding a certain defined magnitude. ... A rectifier is one or more diodes arranged for converting alternating current (AC) to direct current (DC). ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... A switching-mode power supply for laboratory use. ... In telecommunication, a mixer is a nonlinear circuit or device that accepts as its input two different frequencies and presents at its output (a) a signal equal in frequency to the sum of the frequencies of the input signals, (b) a signal equal in frequency to the difference between the... A detector is a device that recovers information of interest contained in a modulated wave. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ... A Step recovery diode (SRD) is a switching diode capable to generate extremely fast voltage pulses when switched quickly from full conduction to reverse polarization. ... A Step recovery diode (SRD) is a switching diode capable to generate extremely fast voltage pulses when switched quickly from full conduction to reverse polarization. ... A Step recovery diode (SRD) is a switching diode capable to generate extremely fast voltage pulses when switched quickly from full conduction to reverse polarization. ... A Cats Whisker is the tiny wire that connects to the detector in a crystal radio. ... For other uses, see Galena (disambiguation). ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... An example of a modern set created by VE6AB The crystal radio receiver (also known as a crystal set) is a passive radio receiver consisting of a variable LC tuned circuit, a diode detector, and audio transducer. ... Layers of a PIN diode PIN diode is a diode with a wide, undoped intrinsic semiconductor region between p-type semiconductor and n-type semiconductor regions. ... Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits... Power electronics is the technology associated with the efficient conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output form. ... Power semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits (switch mode power supplies for example). ... The Insulated Gate Bipolar Transistor combines the simple gate drive characteristics of the MOSFET with the high current and low saturation voltage capability of bipolar transistors by combining an isolated gate FET for the control input, and a bipolar power transistor as a switch, in a single device. ... The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ... Circuit symbol for a thyristor The thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. ... Varicap schematic symbol A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ... A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ... Various types of capacitors A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... A phase-lock, or phase-locked, loop (PLL) is an electronic control system that generates a signal that is locked to the phase of an input or reference signal. ... A frequency-lock, or frequency-locked loop (FLL) is an electronic control system that generates a signal that is locked to the frequency of an input or reference signal. ... A voltage-controlled oscillator or VCO is an electronic oscillator designed to be controlled in oscillation frequency by a voltage input. ... Zener diode schematic symbol A Zener diode is a type of diode that permits current to flow in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger (not equal to, but larger) than the rated breakdown voltage known as Zener knee... Schematic symbols used to denote a bidirectional transient voltage supression diode. ... Clarence Melvin Zener (December 1, 1905 _ July 15, 1993) was the American physicist who first described the electrical property exploited by the Zener diode, which Bell Labs then named after him. ... An avalanche diode is a diode (usually made from silicon, but can be made from another semiconductor) that is designed to break down and conduct at a specified reverse bias voltage. ... A transient voltage suppression diode is a device used to protect sensitive electronics from voltage spikes induced on connected wires. ... Transient means passing with time. ... Photodiode closeup A photodiode A photodiode is a semiconductor diode that functions as a photodetector. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits... A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ... Photopic (black) and scotopic [1] (green) luminosity functions. ... Optical communication is any form of telecommunication that uses light as the transmission medium. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... “LED” redirects here. ... External links LEd Category: TeX ... In semiconductor physics, a direct bandgap means that the minimum of the conduction band lies directly above the maximum of the valence band in momentum space. ... This article is about the chemical compound. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... For other uses, see Wavelength (disambiguation). ... For other uses, see Infrared (disambiguation). ... For other uses, see Ultraviolet (disambiguation). ... For other uses, see Wavelength (disambiguation). ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... An opto-isolator integrated circuit. ... A packaged laser diode with penny for scale. ... A cavity resonator uses resonance to amplify a wave. ... For other uses, see Laser (disambiguation). ... Optical Storage is made possible by data storage devices such as optical discs and holographic storage systems. ... Optical communication is any form of telecommunication that uses light as the transmission medium. ... Esaki A japanese physicist who discovered the tunnel diode ... Tunnel diode schematic symbol A tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave region GHz, by utilizing quantum mechanical effects. ... A VI curve with a negative differential resistance region Negative resistance or negative differential resistance (NDR) is a property of electrical circuit elements composed of certain materials in which, over certain voltage ranges, current is a decreasing function of voltage. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ... A rough approximation of the VI curve for a Gunn diode, showing the negative differential resistance region A Gunn diode, also known as a transferred electron device (TED) is a form of diode used in high-frequency electronics. ... A VI curve with a negative differential resistance region Negative resistance or negative differential resistance (NDR) is a property of electrical circuit elements composed of certain materials in which, over certain voltage ranges, current is a decreasing function of voltage. ... This article is about the type of Electromagnetic radiation. ... Cross coupled LC oscillator with output on top An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. ... The Peltier–Seebeck effect, or thermoelectric effect, is the direct conversion of heat differentials to electric voltage and vice versa. ... A heat engine performs the conversion of heat energy to work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred to the sink from the source, and in this process some of the heat is converted into work. ... Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. ... It has been suggested that Uses of jfet be merged into this article or section. ... Logarithms to various bases: is to base e, is to base , and is to base . ... This article illustrates some typical applications of solid-state integrated circuit operational amplifiers. ...

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). [8] [9] [10] JEDEC stands for Joint Electron Device Engineering Council and is the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA), a trade association that represents all areas of the electronics industry. ...

Related devices

• Transistor
• Thyristor or silicon controlled rectifier (SCR)
• TRIAC
• Diac

Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... Circuit symbol for a thyristor The thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. ... Triac Schematic Symbol A TRIAC, or TRIode for Alternating Current is an electronic component approximately equivalent to two silicon-controlled rectifiers (SCRs/thyristors) joined in inverse parallel (paralleled but with the polarity reversed) and with their gates connected together. ... DIAC For other uses, see DIAC (disambiguation). ...

Applications

Several types of diodes. The scale is centimeters.

Image File history File linksMetadata Download high-resolution version (714x855, 101 KB) A bunch of diodes. ... Image File history File linksMetadata Download high-resolution version (714x855, 101 KB) A bunch of diodes. ...

Radio demodulation

The first use for the diode was the demodulation of amplitude modulated (AM) radio broadcasts. The history of this discovery is treated in depth in the radio article. In summary, an AM signal consists of alternating positive and negative peaks of voltage, whose amplitude or “envelope” is proportional to the original audio signal, but whose average value is zero. The diode (originally a crystal diode) rectifies the AM signal, leaving a signal whose average amplitude is the desired audio signal. The average value is extracted using a simple filter and fed into an audio transducer, which generates sound. Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... It has been suggested that pulse amplitude be merged into this article or section. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... Television signal splitter consisting of a hi-pass filter (left) and a low-pass filter (right). ... A transducer is a device, usually electrical or electronic, that converts one type of energy to another. ...

Power conversion

Rectifiers are constructed from diodes, where they are used to convert alternating current (AC) electricity into direct current (DC). Automotive alternators are a common example, where the diode provides better performance than the commutator of earlier dynamo. Similarly, diodes are also used in Cockcroft-Walton voltage multipliers to convert AC into very high DC voltages. AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... City lights viewed in a motion blurred exposure. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... Early 20th century Alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station. ... In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. ... This article is about machines that produce electricity. ... The Cockcroft-Walton (CW) generator, or multiplier, was named after the two men who in 1932 used this circuit design to power their particle accelerator, performing the first artificial nuclear disintegration in history. ...

Over-voltage protection

Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices. They are usually reverse-biased (non-conducting) under normal circumstances. When the voltage rises above the normal range, the diodes become forward-biased (conducting). For example, diodes are used in ( stepper motor and H-bridge ) motor controller and relay circuits to de-energize coils rapidly without the damaging voltage spikes that would otherwise occur. (Any diode used in such an application is called a flyback diode). Many integrated circuits also incorporate diodes on the connection pins to prevent external voltages from damaging their sensitive transistors. Specialized diodes are used to protect from over-voltages at higher power (see Diode types above). The top electromagnet (1) is charged, attracting the topmost four teeth of a sprocket. ... An H-bridge is an electronic circuit which enables DC electric motors to be run forwards or backwards. ... A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. ... Automotive style miniature relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. ... A switched inductor without and with flyback diode for voltage spike suppression A flyback diode (sometimes called a snubber diode, freewheeling diode, suppressor diode, or catch diode[1]) is a diode used to eliminate flyback, the sudden voltage spike seen across an inductive load when its supply voltage is suddenly... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... Photo of transistor types (tape measure marked in centimeters) Transistor in the SMD form factor The transistor is a solid state semiconductor device used for amplification and switching. ...

Logic gates

Diodes can be combined with other components to construct AND and OR logic gates. This is referred to as diode logic. AND Logic Gate In logic and mathematics, logical conjunction (usual symbol and) is a two-place logical operation that results in a value of true if both of its operands are true, otherwise a value of false. ... OR logic gate. ... A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ... Diode logic is an outdated technology which makes use of diodes to contruct logic gates. ...

Ionising radiation detectors

In addition to light, mentioned above, semiconductor diodes are sensitive to more energetic radiation. In electronics, cosmic rays and other sources of ionising radiation cause noise pulses and single and multiple bit errors. This effect is sometimes exploited by particle detectors to detect radiation. A single particle of radiation, with thousands or millions of electron volts of energy, generates many charge carrier pairs, as its energy is deposited in the semiconductor material. If the depletion layer is large enough to catch the whole shower or to stop a heavy particle, a fairly accurate measurement of the particle’s energy can be made, simply by measuring the charge conducted and without the complexity of a magnetic spectrometer or etc. These semiconductor radiation detectors need efficient and uniform charge collection and low leakage current. They are often cooled by liquid nitrogen. For longer range (about a centimetre) particles they need a very large depletion depth and large area. For short range particles, they need any contact or un-depleted semiconductor on at least one surface to be very thin. The back-bias voltages are near breakdown (around a thousand volts per centimetre). Germanium and silicon are common materials. Some of these detectors sense position as well as energy. They have a finite life, especially when detecting heavy particles, because of radiation damage. Silicon and germanium are quite different in their ability to convert gamma rays to electron showers. A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... This article is about the physical quantity. ... This article is about the engineering discipline. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... This article is about noise as in sound. ... ËŒ For other uses, see Pulse (disambiguation). ... The Compact Muon Solenoid (CMS) is an example of a large particle detector. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about electromagnetic radiation. ...

Semiconductor detectors for high energy particles are used in large numbers. Because of energy loss fluctuations, accurate measurement of the energy deposited is of less use. A semiconductor particle detector is a device that uses a semiconductor (usually silicon) to detect the passage of charged particles. ...

Temperature measuring

A diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature. From the Shockley ideal diode equation given above, it appears the voltage has a positive temperature coefficient (at a constant current)but depends on doping concentration and operating temperature (Sze 2007). The temperature coefficient can be negative as in typical thermistors or positive for temperature sense diodes down to about 20 degrees Kelvin. For other uses, see Temperature (disambiguation). ...

Current steering

Diodes will prevent currents from flowing in unintended directions. To supply power to an electrical circuit during a power failure, the cicuit can draw current from a battery. An Uninterruptible power supply built in this may use diodes to ensure that current is only drawn from the battery when necessary. Similarly, small boats typically have two circuits each with their own battery/batteries: one used for engine starting; one used for domestics. Normally both are charged from a single alternator, and a heavy duty split charge diode is used to prevent the higher charge battery (typically the engine battery) from discharging through the lower charged battery when the alternator is not running [[11]]. Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ... An uninterruptible power supply (UPS), also known as an uninterruptible power source or a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. ...

Additional

Diodes may also be referred to as controlled rectifiers, abbreviated CR on printed wiring boards. Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ...

See also

• Diode modelling
• P-N junction

To meet Wikipedias quality standards, this article or section may require cleanup. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...

Notes

1. ^ 1928 Nobel Prize article on the diode
2. ^ Historical lecture on Karl Braun
3. ^ S. M. Sze, Modern Semiconductor Device Physics, Wiley Interscience, ISBN 0-471-15237-4

External links

• The Unusual Diode FAQ
• Interactive Explanation of Semiconductor Diode
• "Device Cross Section" for pn diode, Schottky diode, and silicon controlled rectifier.