Atransistor is asemiconductor device used toamplify orswitch electrical signals andpower. It is one of the basic building blocks of modernelectronics.[1] It is composed ofsemiconductor material, usually with at least threeterminals for connection to anelectronic circuit. Avoltage orcurrent applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more in miniature form are found embedded inintegrated circuits. Because transistors are the key active components in practically all modernelectronics, many people consider them one of the 20th century's greatest inventions.[2]
Most transistors are made from very puresilicon, and some fromgermanium, but certain other semiconductor materials are sometimes used. A transistor may have only one kind of charge carrier in afield-effect transistor, or may have two kinds of charge carriers inbipolar junction transistor devices. Compared with thevacuum tube, transistors are generally smaller and require less power to operate. Certain vacuum tubes have advantages over transistors at very high operating frequencies or high operating voltages, such astraveling-wave tubes andgyrotrons. Many types of transistors are made to standardized specifications by multiple manufacturers.
Thethermionictriode, avacuum tube invented in 1907, enabled amplifiedradio technology and long-distancetelephony. The triode, however, was a fragile device that consumed a substantial amount of power. In 1909,physicistWilliam Eccles discovered thecrystal diode oscillator.[12] PhysicistJulius Edgar Lilienfeld filed a patent for afield-effect transistor (FET) in Canada in 1925,[13] intended as asolid-state replacement for the triode.[14][15] He filed identical patents in the United States in 1926[16] and 1928.[17][18] However, he did not publish any research articles about his devices nor did his patents cite any specific examples of a working prototype. Because the production of high-qualitysemiconductor materials was still decades away, Lilienfeld's solid-state amplifier ideas would not have found practical use in the 1920s and 1930s, even if such a device had been built.[19] In 1934, inventorOskar Heil patented a similar device in Europe.[20]
From November 17 to December 23, 1947,John Bardeen andWalter Brattain atAT&T'sBell Labs inMurray Hill, New Jersey, performed experiments and observed that when two gold point contacts were applied to a crystal ofgermanium, a signal was produced with the output power greater than the input.[21] Solid State Physics Group leaderWilliam Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge ofsemiconductors. The termtransistor was coined byJohn R. Pierce as a contraction of the termtransresistance.[22][23][24] According toLillian Hoddeson and Vicki Daitch, Shockley proposed that Bell Labs' first patent for a transistor should be based on the field-effect and that he be named as the inventor. Having unearthed Lilienfeld's patents that went into obscurity years earlier, lawyers at Bell Labs advised against Shockley's proposal because the idea of a field-effect transistor that used an electric field as agrid was not new. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the firstpoint-contact transistor.[19] To acknowledge this accomplishment, Shockley, Bardeen and Brattain jointly received the 1956Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect".[25][26]
Shockley's team initially attempted to build a field-effect transistor (FET) by trying to modulate the conductivity of a semiconductor, but was unsuccessful, mainly due to problems with thesurface states, thedangling bond, and thegermanium andcopper compound materials. Trying to understand the mysterious reasons behind this failure led them instead to invent the bipolarpoint-contact andjunction transistors.[27][28]
In 1948, the point-contact transistor was independently invented by physicistsHerbert Mataré andHeinrich Welker while working at theCompagnie des Freins et Signaux Westinghouse, aWestinghouse subsidiary inParis. Mataré had previous experience in developingcrystal rectifiers fromsilicon and germanium in the Germanradar effort duringWorld War II. With this knowledge, he began researching the phenomenon ofinterference in 1947. By June 1948, witnessing currents flowing through point-contacts, he produced consistent results using samples of germanium produced by Welker, similar to what Bardeen and Brattain had accomplished earlier in December 1947. Realizing that Bell Labs' scientists had already invented the transistor, the company rushed to get itstransistron into production for amplified use in France's telephone network, filing his first transistor patent application on August 13, 1948.[29][30][31]
The firstbipolar junction transistors were invented by Bell Labs' William Shockley, who applied for patent (2,569,347) on June 26, 1948. On April 12, 1950, Bell Labs chemistsGordon Teal andMorgan Sparks successfully produced a working bipolar NPN junction amplifying germanium transistor. Bell announced the discovery of this newsandwich transistor in a press release on July 4, 1951.[32][33]
The first high-frequency transistor was thesurface-barrier germanium transistor developed byPhilco in 1953, capable of operating at frequencies up to60 MHz.[34] They were made by etching depressions into an n-type germanium base from both sides with jets ofindium(III) sulfate until it was a few ten-thousandths of an inch thick.Indium electroplated into the depressions formed the collector and emitter.[35][36]
AT&T first used transistors in telecommunications equipment in the No. 4A Toll Crossbar Switching System in 1953, for selecting trunk circuits from routing information encoded on translator cards.[37] Its predecessor, the Western Electric No. 3Aphototransistor, read the mechanical encoding from punched metal cards.
The first prototype pockettransistor radio was shown by INTERMETALL, a company founded byHerbert Mataré in 1952, at theInternationale Funkausstellung Düsseldorf from August 29 to September 6, 1953.[38][39] The first production-model pocket transistor radio was theRegency TR-1, released in October 1954.[26] Produced as a joint venture between the Regency Division of Industrial Development Engineering Associates, I.D.E.A. andTexas Instruments of Dallas, Texas, the TR-1 was manufactured in Indianapolis, Indiana. It was a near pocket-sized radio with four transistors and one germanium diode. The industrial design was outsourced to the Chicago firm of Painter, Teague and Petertil. It was initially released in one of six colours: black, ivory, mandarin red, cloud grey, mahogany and olive green. Other colours shortly followed.[40][41][42]
The first production all-transistor car radio was developed by Chrysler andPhilco corporations and was announced in the April 28, 1955, edition ofThe Wall Street Journal. Chrysler made the Mopar model 914HR available as an option starting in fall 1955 for its new line of 1956 Chrysler and Imperial cars, which reached dealership showrooms on October 21, 1955.[43][44]
TheSony TR-63, released in 1957, was the first mass-produced transistor radio, leading to the widespread adoption of transistor radios.[45] Seven million TR-63s were sold worldwide by the mid-1960s.[46] Sony's success with transistor radios led to transistors replacing vacuum tubes as the dominantelectronic technology in the late 1950s.[47]
The first working silicon transistor was developed at Bell Labs on January 26, 1954, byMorris Tanenbaum. The first production commercial silicon transistor was announced byTexas Instruments in May 1954. This was the work ofGordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs.[48][49][50]
In 1948, Bardeen and Brattain patented the progenitor of MOSFET at Bell Labs, an insulated-gate FET (IGFET) with an inversion layer. Bardeen's patent, and the concept of an inversion layer, forms the basis of CMOS and DRAM technology today.[54]
In the early years of thesemiconductor industry, companies focused on thejunction transistor, a relatively bulky device that was difficult tomass-produce, limiting it to several specialized applications.Field-effect transistors (FETs) were theorized as potential alternatives, but researchers could not get them to work properly, largely due to thesurface state barrier that prevented the externalelectric field from penetrating the material.[55]
Diagram of one of the SiO2 transistor devices made by Frosch and Derrick[7]
In 1955,Carl Frosch and Lincoln Derick accidentally grew a layer of silicon dioxide over the silicon wafer, for which they observed surface passivation effects.[6][56] By 1957 Frosch and Derick, using masking and predeposition, were able to manufacture silicon dioxide field effect transistors; the first planar transistors, in which drain and source were adjacent at the same surface.[7] They showed that silicon dioxide insulated, protected silicon wafers and prevented dopants from diffusing into the wafer.[6][7] After this, J.R. Ligenza and W.G. Spitzer studied the mechanism of thermally grown oxides, fabricated a high quality Si/SiO2 stack and published their results in 1960.[57][58][59]
Following this research,Mohamed Atalla andDawon Kahng proposed a silicon MOS transistor in 1959[60] and successfully demonstrated a working MOS device with their Bell Labs team in 1960.[61][62] Their team included E. E. LaBate and E. I. Povilonis who fabricated the device; M. O. Thurston, L. A. D’Asaro, and J. R. Ligenza who developed the diffusion processes, and H. K. Gummel and R. Lindner who characterized the device.[8][9] With itshigh scalability,[63] much lower power consumption, and higher density than bipolar junction transistors,[64] the MOSFET made it possible to buildhigh-density integrated circuits,[65] allowing the integration of more than 10,000 transistors in a single IC.[66]
Because transistors are the key active components in practically all modernelectronics, many people consider them one of the 20th century's greatest inventions.[2]
The invention of the first transistor at Bell Labs was named anIEEE Milestone in 2009.[75] Other Milestones include the inventions of thejunction transistor in 1948 and the MOSFET in 1959.[76]
The MOSFET is by far the most widely used transistor, in applications ranging fromcomputers andelectronics[77] tocommunications technology such assmartphones.[78] It has been considered the most important transistor,[79] possibly the most important invention in electronics,[80] and the device that enabled modern electronics.[81] It has been the basis of moderndigital electronics since the late 20th century, paving the way for thedigital age.[82] TheUS Patent and Trademark Office calls it a "groundbreaking invention that transformed life and culture around the world".[78] Its ability to bemass-produced by a highly automated process (semiconductor device fabrication), from relatively basic materials, allows astonishingly low per-transistor costs. MOSFETs are the most numerously produced artificial objects in history, with more than 13 sextillion manufactured by 2018.[83]
Although several companies each produce over a billion individually packaged (known asdiscrete) MOS transistors every year,[84] the vast majority are produced inintegrated circuits (also known asICs,microchips, or simplychips), along withdiodes,resistors,capacitors and otherelectronic components, to produce complete electronic circuits. Alogic gate consists of up to about 20 transistors, whereas an advancedmicroprocessor, as of 2023, may contain as many as 134 billion transistors (and for exceptional chips, 2.6 trillion transistors, as of 2020).[85] Transistors are often organized into logic gates in microprocessors to perform computation.[86]
The transistor's low cost, flexibility and reliability have made it ubiquitous. Transistorizedmechatronic circuits have replacedelectromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standardmicrocontroller and write acomputer program to carry out a control function than to design an equivalent mechanical system.
A simple circuit diagram showing the labels of an n–p–n bipolar transistor
A transistor can use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals, a property calledgain. It can produce a stronger output signal, a voltage or current, proportional to a weaker input signal, acting as anamplifier. It can also be used as an electrically controlledswitch, where the amount of current is determined by other circuit elements.[87]
There are two types of transistors, with slight differences in how they are used:
Abipolar junction transistor (BJT) has terminals labeledbase,collector andemitter. A small current at the base terminal, flowing between the base and the emitter, can control or switch a much larger current between the collector and emitter.
Afield-effect transistor (FET) has terminals labeledgate,source anddrain. A voltage at the gate can control a current between source and drain.[88]
The top image in this section represents a typical bipolar transistor in a circuit. A charge flows between emitter and collector terminals depending on the current in the base. Because the base and emitter connections behave like a semiconductor diode, a voltage drop develops between them. The amount of this drop, determined by the transistor's material, is referred to asVBE.[88] (Base Emitter Voltage)
BJT used as an electronic switch in grounded-emitter configuration
Transistors are commonly used indigital circuits aselectronic switches which can be either in anon oroff state, both for high-power applications such asswitched-mode power supplies and for low-power applications such aslogic gates. Important parameters for this application include the current switched, the voltage handled, and the switching speed, characterized by therise and fall times.[88]
In a switching circuit, the goal is to simulate, as near as possible, the ideal switch having the properties of an open circuit when off, the short circuit when on, and an instantaneous transition between the two states. Parameters are chosen such that theoff output is limited to leakage currents too small to affect connected circuitry, the resistance of the transistor in theon state is too small to affect circuitry, and the transition between the two states is fast enough not to have a detrimental effect.[88]
In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the emitter and collector currents rise exponentially. The collector voltage drops because of reduced resistance from the collector to the emitter. If the voltage difference between the collector and emitter were zero (or near zero), the collector current would be limited only by the load resistance (light bulb) and the supply voltage. This is calledsaturation because the current is flowing from collector to emitter freely. When saturated, the switch is said to beon.[89]
The use of bipolar transistors for switching applications requires biasing the transistor so that it operates between its cut-off region in the off-state and the saturation region (on). This requires sufficient base drive current. As the transistor provides current gain, it facilitates the switching of a relatively large current in the collector by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example of a light-switch circuit, as shown, the resistor is chosen to provide enough base current to ensure the transistor is saturated.[88] The base resistor value is calculated from the supply voltage, transistor C-E junction voltage drop, collector current, and amplification factor beta.[90]
An amplifier circuit, a common-emitter configuration with a voltage-divider bias circuit
Thecommon-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor whose current amplification combined with the properties of the circuit means that small swings inVin produce large changes inVout.[88]
Various configurations of single transistor amplifiers are possible, with some providing current gain, some voltage gain, and some both.
Frommobile phones totelevisions, vast numbers of products include amplifiers forsound reproduction,radio transmission, andsignal processing. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.[88]
Modern transistor audio amplifiers of up to a few hundredwatts are common and relatively inexpensive.
Before transistors were developed,vacuum (electron) tubes (or in the UKthermionic valves or justvalves) were the main active components in electronic equipment.
The key advantages that have allowed transistors to replace vacuum tubes in most applications are
No cathode heater (which produces the characteristic orange glow of tubes), reducing power consumption, eliminating delay as tube heaters warm up, and immune fromcathode poisoning and depletion.
Very small size and weight, reducing equipment size.
Large numbers of extremely small transistors can be manufactured as a singleintegrated circuit.
Low operating voltages compatible with batteries of only a few cells.
Circuits with greater energy efficiency are usually possible. For low-power applications (for example, voltage amplification) in particular, energy consumption can be very much less than for tubes.
Complementary devices available, providing design flexibility including complementary-symmetry circuits, not possible with vacuum tubes.
Very low sensitivity to mechanical shock and vibration, providing physical ruggedness and virtually eliminating shock-induced spurious signals (for example,microphonics in audio applications).
Not susceptible to breakage of a glass envelope, leakage, outgassing, and other physical damage.
They lack the higherelectron mobility afforded by the vacuum of vacuum tubes, which is desirable for high-power, high-frequency operation – such as that used in some over-the-airtelevision transmitters and intravelling-wave tubes used as amplifiers in some satellites
Transistors and other solid-state devices are susceptible to damage from very brief electrical and thermal events, includingelectrostatic discharge in handling. Vacuum tubes are electrically much more rugged.
In audio applications, transistors lack the lower-harmonic distortion – the so-calledtube sound – which is characteristic of vacuum tubes, and is preferred by some.[91]
Maximum operating frequency: low, medium, high,radio (RF),microwave frequency (the maximum effective frequency of a transistor in a common-emitter or common-source circuit is denoted by the termfT, an abbreviation fortransition frequency—the frequency at which the transistor yields unity voltage gain)
Application: switch, general purpose, audio,high voltage, super-beta, matched pair.
Working temperature: Extreme temperature transistors and traditional temperature transistors (−55 to 150 °C (−67 to 302 °F)). Extreme temperature transistors include high-temperature transistors (above 150 °C (302 °F)) and low-temperature transistors (below −55 °C (−67 °F)). The high-temperature transistors that operate thermally stable up to 250 °C (482 °F) can be developed by a general strategy of blending interpenetrating semi-crystalline conjugated polymers and high glass-transition temperature insulating polymers.[93]
Hence, a particular transistor may be described assilicon, surface-mount, BJT, NPN, low-power, high-frequency switch.
Convenientmnemonic to remember the type of transistor (represented by anelectrical symbol) involves the direction of the arrow. For theBJT, on ann–p–n transistor symbol, the arrow will "NotPoint iN". On ap–n–p transistor symbol, the arrow "Points iNProudly". However, this does not apply to MOSFET-based transistor symbols as the arrow is typically reversed (i.e. the arrow for the n–p–n points inside).
Operation of anFET and itsId-Vg curve. At first, when no gate voltage is applied, there are no inversion electrons in the channel, so the device is turned off. As gate voltage increases, the inversion electron density in the channel increases, the current increases, and the device turns on.
Thefield-effect transistor, sometimes called aunipolar transistor, uses either electrons (inn-channel FET) or holes (inp-channel FET) for conduction. The four terminals of the FET are namedsource,gate,drain, andbody (substrate). On most FETs, the body is connected to the source inside the package, and this will be assumed for the following description.
In a FET, the drain-to-source current flows via a conducting channel that connects thesource region to thedrain region. The conductivity is varied by the electric field that is produced when a voltage is applied between the gate and source terminals, hence the current flowing between the drain and source is controlled by the voltage applied between the gate and source. As the gate–source voltage (VGS) is increased, the drain–source current (IDS) increases exponentially forVGS below threshold, and then at a roughly quadratic rate: (IDS ∝ (VGS −VT)2, whereVT is the threshold voltage at which drain current begins)[94] in thespace-charge-limited region above threshold. A quadratic behavior is not observed in modern devices, for example, at the65 nm technology node.[95]
For low noise at narrowbandwidth, the higher input resistance of the FET is advantageous.
FETs are divided into two families:junction FET (JFET) andinsulated gate FET (IGFET). The IGFET is more commonly known as ametal–oxide–semiconductor FET (MOSFET), reflecting its original construction from layers of metal (the gate), oxide (the insulation), and semiconductor. Unlike IGFETs, the JFET gate forms ap–n diode with the channel which lies between the source and drains. Functionally, this makes the n-channel JFET the solid-state equivalent of the vacuum tubetriode which, similarly, forms a diode between itsgrid andcathode. Also, both devices operate in thedepletion-mode, they both have a high input impedance, and they both conduct current under the control of an input voltage.
Metal–semiconductor FETs (MESFETs) are JFETs in which thereverse biased p–n junction is replaced by ametal–semiconductor junction. These, and the HEMTs (high-electron-mobility transistors, or HFETs), in which a two-dimensional electron gas with very high carrier mobility is used for charge transport, are especially suitable for use at very high frequencies (several GHz).
FETs are further divided intodepletion-mode andenhancement-mode types, depending on whether the channel is turned on or off with zero gate-to-source voltage. For enhancement mode, the channel is off at zero bias, and a gate potential canenhance the conduction. For the depletion mode, the channel is on at zero bias, and a gate potential (of the opposite polarity) candeplete the channel, reducing conduction. For either mode, a more positive gate voltage corresponds to a higher current for n-channel devices and a lower current for p-channel devices. Nearly all JFETs are depletion-mode because the diode junctions would forward bias and conduct if they were enhancement-mode devices, while most IGFETs are enhancement-mode types.
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS),[65] is a type of field-effect transistor that isfabricated by thecontrolled oxidation of a semiconductor, typicallysilicon. It has an insulatedgate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronicsignals. The MOSFET is by far the most common transistor, and the basic building block of most modernelectronics.[82] The MOSFET accounts for 99.9% of all transistors in the world.[96]
Bipolar transistors are so named because they conduct by using both majority and minoritycarriers. The bipolar junction transistor, the first type of transistor to be mass-produced, is a combination of two junction diodes and is formed of either a thin layer of p-type semiconductor sandwiched between two n-type semiconductors (an n–p–n transistor), or a thin layer of n-type semiconductor sandwiched between two p-type semiconductors (a p–n–p transistor). This construction produces twop–n junctions: a base-emitter junction and a base-collector junction, separated by a thin region of semiconductor known as the base region. (Two junction diodes wired together without sharing an intervening semiconducting region will not make a transistor.)
BJTs have three terminals, corresponding to the three layers of semiconductor—anemitter, abase, and acollector. They are useful inamplifiers because the currents at the emitter and collector are controllable by a relatively small base current.[97] In an n–p–n transistor operating in the active region, the emitter-base junction is forward-biased (electrons andholes recombine at the junction), and the base-collector junction is reverse-biased (electrons and holes are formed at, and move away from, the junction), and electrons are injected into the base region. Because the base is narrow, most of these electrons will diffuse into the reverse-biased base-collector junction and be swept into the collector; perhaps one-hundredth of the electrons will recombine in the base, which is the dominant mechanism in the base current. As well, as the base is lightly doped (in comparison to the emitter and collector regions), recombination rates are low, permitting more carriers to diffuse across the base region. By controlling the number of electrons that can leave the base, the number of electrons entering the collector can be controlled.[97] Collector current is approximately β (common-emitter current gain) times the base current. It is typically greater than 100 for small-signal transistors but can be smaller in transistors designed for high-power applications.
Unlike the field-effect transistor (see below), the BJT is a low-input-impedance device. Also, as the base-emitter voltage (VBE) is increased the base-emitter current and hence the collector-emitter current (ICE) increase exponentially according to theShockley diode model and theEbers-Moll model. Because of this exponential relationship, the BJT has a highertransconductance than the FET.
Bipolar transistors can be made to conduct by exposure to light because the absorption of photons in the base region generates a photocurrent that acts as a base current; the collector current is approximately β times the photocurrent. Devices designed for this purpose have a transparent window in the package and are calledphototransistors.
TheMOSFET is by far the most widely used transistor for bothdigital circuits as well asanalog circuits,[98] accounting for 99.9% of all transistors in the world.[96] Thebipolar junction transistor (BJT) was previously the most commonly used transistor during the 1950s to 1960s. Even after MOSFETs became widely available in the 1970s, the BJT remained the transistor of choice for many analog circuits such as amplifiers because of their greater linearity, up until MOSFET devices (such aspower MOSFETs,LDMOS andRF CMOS) replaced them for mostpower electronic applications in the 1980s. Inintegrated circuits, the desirable properties of MOSFETs allowed them to capture nearly all market share for digital circuits in the 1970s. Discrete MOSFETs (typically power MOSFETs) can be applied in transistor applications, including analog circuits, voltage regulators, amplifiers, power transmitters, and motor drivers.
GAAFET, Similar to FinFET but nanowires are used instead of fins, the nanowires are stacked vertically and are surrounded on 4 sides by the gate
MBCFET, a variant of GAAFET that uses horizontal nanosheets instead of nanowires, made by Samsung. Also known as RibbonFET (made by Intel) and as horizontal nanosheet transistor.
Thin-film transistor (TFT), used inLCD andOLED displays, types include amorphous silicon, LTPS, LTPO and IGZO transistors
ADarlington transistor with the upper case removed so the transistor chip (the small square) can be seen. It is effectively two transistors on the same chip. One is much larger than the other, but both are large in comparison to transistors inlarge-scale integration because this particular example is intended for power applications.Darlington transistors are two BJTs connected together to provide a high current gain equal to the product of the current gains of the two transistors
Insulated-gate bipolar transistors (IGBTs) use a medium-power IGFET, similarly connected to a power BJT, to give a high input impedance. Power diodes are often connected between certain terminals depending on specific use. IGBTs are particularly suitable for heavy-duty industrial applications. TheASEA Brown Boveri (ABB)5SNA2400E170100 ,[99] intended for three-phase power supplies, houses three n–p–n IGBTs in a case measuring 38 by 140 by 190 mm and weighing 1.5 kg. Each IGBT is rated at 1,700 volts and can handle 2,400 amperes
Emitter-switched bipolar transistor (ESBT) is a monolithic configuration of a high-voltage bipolar transistor and a low-voltage power MOSFET incascode topology. It was introduced by STMicroelectronics in the 2000s,[100] and abandoned a few years later around 2012.[101]
Multiple-base transistor, used to amplify very-low-level signals in noisy environments such as the pickup of arecord player orradio front ends. Effectively, it is a very large number of transistors in parallel where, at the output, the signal is added constructively, but random noise is added onlystochastically.[102]
Diffusion transistor, formed by diffusing dopants into semiconductor substrate; can be both BJT and FET.
Unijunction transistor, which can be used as a simple pulse generator. It comprises the main body of either p-type or n-type semiconductor with ohmic contacts at each end (terminalsBase1 andBase2). A junction with the opposite semiconductor type is formed at a point along the length of the body for the third terminal (Emitter).
Single-electron transistors (SET), consist of a gate island between two tunneling junctions. The tunneling current is controlled by a voltage applied to the gate through a capacitor.[103]
Junctionless nanowire transistor (JNT), uses a simple nanowire of silicon surrounded by an electrically isolatedwedding ring that acts to gate the flow of electrons through the wire.
Nanoscale vacuum-channel transistor, when in 2012, NASA and the National Nanofab Center in South Korea were reported to have built a prototype vacuum-channel transistor in only 150 nanometers in size, can be manufactured cheaply using standard silicon semiconductor processing, can operate at high speeds even in hostile environments, and could consume just as much power as a standard transistor.[105]
Three major identification standards are used for designating transistor devices. In each, the alphanumeric prefix provides clues to the type of the device.
TheJEDEC part numbering scheme evolved in the 1960s in the United States. The JEDECEIA-370 transistor device numbers usually start with2N, indicating a three-terminal device.[113] Dual-gatefield-effect transistors are four-terminal devices, and begin with 3N. The prefix is followed by a two-, three- or four-digit number with no significance as to device properties, although early devices with low numbers tend to be germanium devices. For example,2N3055 is a silicon n–p–n power transistor, 2N1301 is a p–n–p germanium switching transistor. A letter suffix, such as A, is sometimes used to indicate a newer variant, but rarely gain groupings.
In Japan, theJIS semiconductor designation (|JIS-C-7012), labels transistor devices starting with2S,[114] e.g., 2SD965, but sometimes the 2S prefix is not marked on the package–a 2SD965 might only be markedD965 and a 2SC1815 might be listed by a supplier as simplyC1815. This series sometimes has suffixes, such as R, O, BL, standing for red, orange, blue, etc., to denote variants, such as tighterhFE (gain) groupings.
JIS transistor prefix table
Prefix
Type and usage
2SA
high-frequency p–n–p BJT
2SB
audio-frequency p–n–p BJT
2SC
high-frequency n–p–n BJT
2SD
audio-frequency n–p–n BJT
2SJ
P-channel FET (both JFET and MOSFET)
2SK
N-channel FET (both JFET and MOSFET)
European Electronic Component Manufacturers Association (EECA)
The European Electronic Component Manufacturers Association (EECA) uses a numbering scheme that was inherited fromPro Electron when it merged with EECA in 1983. This scheme begins with two letters: the first gives the semiconductor type (A for germanium, B for silicon, and C for materials like GaAs); the second letter denotes the intended use (A for diode, C for general-purpose transistor, etc.). A three-digit sequence number (or one letter and two digits, for industrial types) follows. With early devices this indicated the case type. Suffixes may be used, with a letter (e.g. C often means highhFE, such as in: BC549C[115]) or other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A[116]). The more common prefixes are:
Manufacturers of devices may have their proprietary numbering system, for exampleCK722. Since devices aresecond-sourced, a manufacturer's prefix (like MPF in MPF102, which originally would denote aMotorolaFET) now is an unreliable indicator of who made the device. Some proprietary naming schemes adopt parts of other naming schemes, for example, a PN2222A is a (possiblyFairchild Semiconductor) 2N2222A in a plastic case (but a PN108 is a plastic version of a BC108, not a 2N108, while the PN100 is unrelated to other xx100 devices).
Manufacturers buying large numbers of similar parts may have them supplied withhouse numbers, identifying a particular purchasing specification and not necessarily a device with a standardized registered number. For example, an HP part 1854,0053 is a (JEDEC) 2N2218 transistor[117][118] which is also assigned the CV number: CV7763[119]
With so many independent naming schemes, and the abbreviation of part numbers when printed on the devices, ambiguity sometimes occurs. For example, two different devices may be marked J176 (one the J176 low-powerJFET, the other the higher-poweredMOSFET 2SJ176).
As older through-hole transistors are given surface-mount packaged counterparts, they tend to be assigned many different part numbers because manufacturers have their systems to cope with the variety inpinout arrangements and options for dual or matched n–p–n + p–n–p devices in one pack. So even when the original device (such as a 2N3904) may have been assigned by a standards authority, and well known by engineers over the years, the new versions are far from standardized in their naming.
The first BJTs were made fromgermanium (Ge).Silicon (Si) types currently predominate but certain advanced microwave and high-performance versions now employ thecompound semiconductor materialgallium arsenide (GaAs) and thesemiconductor alloysilicon–germanium (SiGe). Single-element semiconductor material (Ge and Si) is described aselemental.
Rough parameters for the most common semiconductor materials used to make transistors are given in the adjacent table. These parameters will vary with an increase in temperature, electric field, impurity level, strain, and sundry other factors.
Thejunction forward voltage is the voltage applied to the emitter-base junction of a BJT to make the base conduct a specified current. The current increases exponentially as the junction forward voltage is increased. The values given in the table are typical for a current of 1 mA (the same values apply to semiconductor diodes). The lower the junction forward voltage the better, as this means that less power is required to drive the transistor. The junction forward voltage for a given current decreases with an increase in temperature. For a typical silicon junction, the change is −2.1 mV/°C.[120] In some circuits special compensating elements (sensistors) must be used to compensate for such changes.
The density of mobile carriers in the channel of a MOSFET is a function of the electric field forming the channel and of various other phenomena such as the impurity level in the channel. Some impurities, called dopants, are introduced deliberately in making a MOSFET, to control the MOSFET electrical behavior.
Theelectron mobility andhole mobility columns show the average speed that electrons and holes diffuse through the semiconductor material with anelectric field of 1 volt per meter applied across the material. In general, the higher the electron mobility the faster the transistor can operate. The table indicates that Ge is a better material than Si in this respect. However, Ge has four major shortcomings compared to silicon and gallium arsenide:
It is less suitable for fabricating integrated circuits.
Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolarn–p–n transistor tends to be swifter than an equivalentp–n–p transistor. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high-frequency applications. A relatively recent[when?] FET development, thehigh-electron-mobility transistor (HEMT), has aheterostructure (junction between different semiconductor materials) of aluminium gallium arsenide (AlGaAs)-gallium arsenide (GaAs) which has twice the electron mobility of a GaAs-metal barrier junction. Because of their high speed and low noise, HEMTs are used in satellite receivers working at frequencies around 12 GHz. HEMTs based ongallium nitride andaluminum gallium nitride (AlGaN/GaN HEMTs) provide still higher electron mobility and are being developed for various applications.
Maximumjunction temperature values represent a cross-section taken from various manufacturers' datasheets. This temperature should not be exceeded or the transistor may be damaged.
Al–Si junction refers to the high-speed (aluminum-silicon) metal–semiconductor barrier diode, commonly known as aSchottky diode. This is included in the table because some silicon power IGFETs have aparasitic reverse Schottky diode formed between the source and drain as part of the fabrication process. This diode can be a nuisance, but sometimes it is used in the circuit.
Discrete transistors can be individually packaged transistors or unpackaged transistor chips.
Transistors come in many differentsemiconductor packages (see image). The two main categories arethrough-hole (orleaded), andsurface-mount, also known assurface-mount device (SMD). Theball grid array (BGA) is the latest surface-mount package. It has solder balls on the underside in place of leads. Because they are smaller and have shorter interconnections, SMDs have better high-frequency characteristics but lower power ratings.
Transistor packages are made of glass, metal, ceramic, or plastic. The package often dictates the power rating and frequency characteristics. Power transistors have larger packages that can be clamped toheat sinks for enhanced cooling. Additionally, most power transistors have the collector or drain physically connected to the metal enclosure. At the other extreme, some surface-mountmicrowave transistors are as small as grains of sand.
Often a given transistor type is available in several packages. Transistor packages are mainly standardized, but the assignment of a transistor's functions to the terminals is not: other transistor types can assign other functions to the package's terminals. Even for the same transistor type the terminal assignment can vary (normally indicated by a suffix letter to the part number, q.e. BC212L and BC212K).
Nowadays most transistors come in a wide range of SMT packages. In comparison, the list of available through-hole packages is relatively small. Here is a short list of the most common through-hole transistors packages in alphabetical order:ATV, E-line, MRT, HRT, SC-43, SC-72, TO-3, TO-18, TO-39, TO-92, TO-126, TO220, TO247, TO251, TO262, ZTX851.
Unpackaged transistor chips (die) may be assembled into hybrid devices.[121] TheIBM SLT module of the 1960s is one example of such a hybrid circuit module using glass passivated transistor (and diode) die. Other packaging techniques for discrete transistors as chips includedirect chip attach (DCA) andchip-on-board (COB).[121]
^abLilienfeld, Julius Edgar, "Method and apparatus for controlling electric current"U.S. patent 1,745,175 January 28, 1930 (filed in Canada 1925-10-22, in US October 8, 1926).
^FR 1010427 H. F. Mataré / H. Welker / Westinghouse: "Nouveau sytème crystallin à plusieur électrodes réalisant des relais de effects électroniques" filed on August 13, 1948
^US 2673948 H. F. Mataré / H. Welker / Westinghouse, "Crystal device for controlling electric currents by means of a solid semiconductor" French priority August 13, 1948
^Bradley, W.E. (December 1953). "The Surface-Barrier Transistor: Part I-Principles of the Surface-Barrier Transistor".Proceedings of the IRE.41 (12):1702–1706.doi:10.1109/JRPROC.1953.274351.S2CID51652314.
^The Wall Street Journal, December 4, 1953, page 4, Article "Philco Claims Its Transistor Outperforms Others Now In Use"
^Electronics magazine, January 1954, Article "Electroplated Transistors Announced"
^P. Mallery,Transistors and Their Circuits in the 4A Toll Crossbar Switching System, AIEE Transactions, September 1953, p.388
^Chelikowski, J. (2004) "Introduction: Silicon in all its Forms", p. 1 inSilicon: evolution and future of a technology. P. Siffert and E. F. Krimmel (eds.). Springer,ISBN3-540-40546-1.
^McFarland, Grant (2006)Microprocessor design: a practical guide from design planning to manufacturing. McGraw-Hill Professional. p. 10.ISBN0-07-145951-0.
^Lilienfeld, Julius Edgar, "Device for controlling electric current"U.S. patent 1,900,018 March 7, 1933 (filed in US March 28, 1928).
^Grundmann, Marius (2010).The Physics of Semiconductors. Springer-Verlag.ISBN978-3-642-13884-3.
^D. Kahng and S. M. Sze, "A floating gate and its application to memory devices",The Bell System Technical Journal, vol. 46, no. 4, 1967, pp. 1288–1295
^Thompson, S. E.; Chau, R. S.; Ghani, T.; Mistry, K.; Tyagi, S.; Bohr, M. T. (2005). "In search of "Forever," continued transistor scaling one new material at a time".IEEE Transactions on Semiconductor Manufacturing.18 (1):26–36.doi:10.1109/TSM.2004.841816.ISSN0894-6507.S2CID25283342.In the field of electronics, the planar Si metal–oxide–semiconductor field-effect transistor (MOSFET) is perhaps the most important invention.
^Buonomo, S.; Ronsisvalle, C.; Scollo, R.;STMicroelectronics; Musumeci, S.; Pagano, R.; Raciti, A.;University of Catania Italy (October 16, 2003).IEEE (ed.).A new monolithic emitter-switching bipolar transistor (ESBT) in high-voltage converter applications. 38th IAS annual Meeting on Conference Record of the Industry Applications Conference. Vol. 3 of 3. Salt Lake City. pp. 1810–1817.doi:10.1109/IAS.2003.1257745.
^STMicroelectronics."ESBTs".www.st.com. RetrievedFebruary 17, 2019.ST no longer offers these components, this web page is empty, and datasheets are obsoletes
^Zhong Yuan Chang, Willy M. C. Sansen,Low-Noise Wide-Band Amplifiers in Bipolar and CMOS Technologies, page 31, Springer, 1991ISBN0792390962.
Amos SW, James MR (1999).Principles of Transistor Circuits. Butterworth-Heinemann.ISBN978-0-7506-4427-3.
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