A transistor is a semiconductor device used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics.<ref>"Transistor". Britannica. Retrieved January 12, 2021.</ref> It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current 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 in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.<ref name="auto1">"A History of the Invention of the Transistor and Where It Will Lead Us"(PDF). IEEE JOURNAL OF SOLID-STATE CIRCUITS Vol 32 No 12. December 1997.</ref>
Most transistors are made from very pure silicon, and some from germanium, but certain other semiconductor materials are sometimes used. A transistor may have only one kind of charge carrier in a field-effect transistor, or may have two kinds of charge carriers in bipolar junction transistor devices. Compared with the vacuum 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 as Traveling-wave tubes and Gyrotrons. Many types of transistors are made to standardized specifications by multiple manufacturers.
From November 17 to December 23, 1947, John Bardeen and Walter Brattain at AT&T's Bell Labs in Murray Hill, New Jersey, performed experiments and observed that when two gold point contacts were applied to a crystal of germanium, a signal was produced with the output power greater than the input.<ref>"November 17 – December 23, 1947: Invention of the First Transistor". American Physical Society. Archived from the original on January 20, 2013.</ref> Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term transistor was coined by John R. Pierce as a contraction of the term transresistance.<ref>Millman, S., ed. (1983). A History of Engineering and Science in the Bell System, Physical Science (1925–1980). AT&T Bell Laboratories. p. 102.</ref><ref>Bodanis, David (2005). Electric Universe. Crown Publishers, New York. ISBN978-0-7394-5670-5.</ref><ref>"transistor". American Heritage Dictionary (3rd ed.). Boston: Houghton Mifflin. 1992.</ref> According to Lillian 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 a "grid" was not new. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first point-contact transistor.<ref name="todaysengineer.org"/> To acknowledge this accomplishment, Shockley, Bardeen and Brattain jointly received the 1956 Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect".<ref>"The Nobel Prize in Physics 1956". nobelprize.org. Archived from the original on March 12, 2007.</ref><ref name="Guarnieri 1">Guarnieri, M. (2017). "Seventy Years of Getting Transistorized". IEEE Industrial Electronics Magazine. 11 (4): 33–37. doi:10.1109/MIE.2017.2757775. hdl:11577/3257397. S2CID38161381.</ref>
In 1948, the point-contact transistor was independently invented by physicists Herbert Mataré and Heinrich Welker while working at the Compagnie des Freins et Signaux Westinghouse, a Westinghouse subsidiary in Paris. Mataré had previous experience in developing crystal rectifiers from silicon and germanium in the German radar effort during World War II. With this knowledge, he began researching the phenomenon of "interference" 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 its "transistron" into production for amplified use in France's telephone network, filing his first transistor patent application on August 13, 1948.<ref>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</ref><ref>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</ref><ref>"1948, The European Transistor Invention". Computer History Museum. Archived from the original on September 29, 2012.</ref>
The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating at frequencies up to 60 MHz.<ref>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.</ref> They were made by etching depressions into an n-type germanium base from both sides with jets of Indium(III) sulfate until it was a few ten-thousandths of an inch thick. Indium electroplated into the depressions formed the collector and emitter.<ref>The Wall Street Journal, December 4, 1953, page 4, Article "Philco Claims Its Transistor Outperforms Others Now In Use"</ref><ref>Electronics magazine, January 1954, Article "Electroplated Transistors Announced"</ref>
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.<ref>P. Mallery, Transistors and Their Circuits in the 4A Toll Crossbar Switching System, AIEE Transactions, September 1953, p.388</ref> Its predecessor, the Western Electric No. 3A phototransistor, read the mechanical encoding from punched metal cards.
The first prototype pocket transistor radio was shown by INTERMETALL, a company founded by Herbert Mataré in 1952, at the Internationale Funkausstellung Düsseldorf from August 29 to September 6, 1953.<ref>1953 Foreign Commerce Weekly; Volume 49; pp.23</ref><ref>"Der deutsche Erfinder des Transistors – Nachrichten Welt Print – DIE WELT". Die Welt. Welt.de. November 23, 2011. Archived from the original on May 15, 2016. Retrieved May 1, 2016.</ref> The first production-model pocket transistor radio was the Regency TR-1, released in October 1954.<ref name="Guarnieri 1" /> Produced as a joint venture between the Regency Division of Industrial Development Engineering Associates, I.D.E.A. and Texas 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.<ref>"Regency TR-1 Transistor Radio History". Archived from the original on October 21, 2004. Retrieved April 10, 2006.</ref><ref>"The Regency TR-1 Family". Archived from the original on April 27, 2017. Retrieved April 10, 2017.</ref><ref>"Regency manufacturer in USA, radio technology from United St". Archived from the original on April 10, 2017. Retrieved April 10, 2017.</ref>
The first production all-transistor car radio was developed by Chrysler and Philco corporations and was announced in the April 28, 1955, edition of The 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.<ref>Wall Street Journal, "Chrysler Promises Car Radio With Transistors Instead of Tubes in '56", April 28, 1955, page 1</ref><ref>"FCA North America - Historical Timeline 1950-1959". www.fcanorthamerica.com. Archived from the original on April 2, 2015. Retrieved December 5, 2017.</ref>
The first working silicon transistor was developed at Bell Labs on January 26, 1954, by Morris Tanenbaum. The first production commercial silicon transistor was announced by Texas Instruments in May 1954. This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs.<ref>Riordan, Michael (May 2004). "The Lost History of the Transistor". IEEE Spectrum: 48–49. Archived from the original on May 31, 2015.</ref><ref>Chelikowski, J. (2004) "Introduction: Silicon in all its Forms", p. 1 in Silicon: evolution and future of a technology. P. Siffert and E. F. Krimmel (eds.). Springer, ISBN3-540-40546-1.</ref><ref>McFarland, Grant (2006) Microprocessor design: a practical guide from design planning to manufacturing. McGraw-Hill Professional. p. 10. ISBN0-07-145951-0.</ref>
The basic principle of the field-effect transistor (FET) was first proposed by physicist Julius Edgar Lilienfeld when he filed a patent for a device similar to MESFET in 1926, and for an insulated-gate field-effect transistor in 1928.<ref name="auto"/><ref>Lilienfeld, Julius Edgar, "Device for controlling electric current" U.S. patent 1,900,018 March 7, 1933 (filed in US March 28, 1928).</ref> The FET concept was later also theorized by engineer Oskar Heil in the 1930s and by William Shockley in the 1940s.
In 1945 JFET was patented by Heinrich Welker.<ref>Grundmann, Marius (2010). The Physics of Semiconductors. Springer-Verlag. ISBN978-3-642-13884-3.</ref> Following Shockley's theoretical treatment on JFET in 1952, a working practical JFET was made in 1953 by George C. Dacey and Ian M. Ross.<ref>Junction Field-Effect Devices, Semiconductor Devices for Power Conditioning, 1982.</ref>
In 1948, Bardeen patented the progenitor of MOSFET, an insulated-gate FET (IGFET) with an inversion layer. Bardeen's patent, and the concept of an inversion layer, forms the basis of CMOS technology today.<ref>Howard R. Duff (2001). "John Bardeen and transistor physics". AIP Conference Proceedings. Vol. 550. pp. 3–32. doi:10.1063/1.1354371.</ref>
Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.<ref name="auto1"/>
The transistor's low cost, flexibility and reliability have made it ubiquitous. Transistorized mechatronic circuits have replaced electromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical system.
Simplified operation
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 called gain. It can produce a stronger output signal, a voltage or current, proportional to a weaker input signal, acting as an amplifier. It can also be used as an electrically controlled switch, where the amount of current is determined by other circuit elements.<ref>Roland, James (August 1, 2016). How Transistors Work. Lerner Publications. ISBN978-1-5124-2146-0.</ref>
There are two types of transistors, with slight differences in how they are used:
A bipolar junction transistor (BJT) has terminals labeled base, collector and emitter. 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.
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 as VBE.<ref name="Pulfrey" />
Transistor as a switch
BJT used as an electronic switch in grounded-emitter configuration
Transistors are commonly used in digital circuits as electronic switches which can be either in an "on" or "off" state, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates. Important parameters for this application include the current switched, the voltage handled, and the switching speed, characterized by the rise and fall times.<ref name="Pulfrey" />
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 the "off" output is limited to leakage currents too small to affect connected circuitry, the resistance of the transistor in the "on" state is too small to affect circuitry, and the transition between the two states is fast enough not to have a detrimental effect.<ref name="Pulfrey" />
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 called saturation because the current is flowing from collector to emitter freely. When saturated, the switch is said to be on.<ref>Kaplan, Daniel (2003). Hands-On Electronics. pp. 47–54, 60–61. Bibcode:2003hoe..book.....K. ISBN978-0-511-07668-8.</ref>
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.<ref name="Pulfrey" /> The base resistor value is calculated from the supply voltage, transistor C-E junction voltage drop, collector current, and amplification factor beta.<ref>"Transistor Base Resistor Calculator". January 27, 2012.</ref>
Transistor as an amplifier
An amplifier circuit, a common-emitter configuration with a voltage-divider bias circuit
The common-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 in Vin produce large changes in Vout.<ref name="Pulfrey" />
Various configurations of single transistor amplifiers are possible, with some providing current gain, some voltage gain, and some both.
From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal 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.<ref name="Pulfrey" />
Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.
Comparison with vacuum tubes
Before transistors were developed, vacuum (electron) tubes (or in the UK "thermionic valves" or just "valves") were the main active components in electronic equipment.
Advantages
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 from cathode poisoning and depletion.
Very small size and weight, reducing equipment size.
Large numbers of extremely small transistors can be manufactured as a single integrated 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.
Limitations
Transistors may have the following limitations:
They lack the higher electron 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-air television transmitters and in travelling 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, including electrostatic discharge in handling. Vacuum tubes are electrically much more rugged.
In audio applications, transistors lack the lower-harmonic distortion – the so-called tube sound – which is characteristic of vacuum tubes, and is preferred by some.<ref name=Veen1>van der Veen, M. (2005). "Universal system and output transformer for valve amplifiers"(PDF). 118th AES Convention, Barcelona, Spain. Archived(PDF) from the original on December 29, 2009.</ref>
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 term fT, an abbreviation for transition 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.<ref>Gumyusenge, Aristide; Tran, Dung T.; Luo, Xuyi; Pitch, Gregory M.; Zhao, Yan; Jenkins, Kaelon A.; Dunn, Tim J.; Ayzner, Alexander L.; Savoie, Brett M.; Mei, Jianguo (December 7, 2018). "Semiconducting polymer blends that exhibit stable charge transport at high temperatures". Science. 362 (6419): 1131–1134. Bibcode:2018Sci...362.1131G. doi:10.1126/science.aau0759. ISSN0036-8075. PMID30523104.</ref>
Hence, a particular transistor may be described as silicon, surface-mount, BJT, NPN, low-power, high-frequency switch.
Mnemonics
Convenient mnemonic to remember the type of transistor (represented by an electrical symbol) involves the direction of the arrow. For the BJT, on an n-p-n transistor symbol, the arrow will "Not Point iN". On a p-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 an FET and its Id-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.
The field-effect transistor, sometimes called a unipolar transistor, uses either electrons (in n-channel FET) or holes (in p-channel FET) for conduction. The four terminals of the FET are named source, gate, drain, and body (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 the source region to the drain 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 for VGS below threshold, and then at a roughly quadratic rate: (IDS ∝ (VGS − VT)2, where VT is the threshold voltage at which drain current begins)<ref name=horowitz-hill>Horowitz, Paul; Winfield Hill (1989). The Art of Electronics (2nd ed.). Cambridge University Press. p. [115]. ISBN978-0-521-37095-0.</ref> in the "space-charge-limited" region above threshold. A quadratic behavior is not observed in modern devices, for example, at the 65 nm technology node.<ref name=Sansen>
Sansen, W. M. C. (2006). Analog design essentials. New York, Berlin: Springer. p. §0152, p. 28. ISBN978-0-387-25746-4.</ref>
For low noise at narrow bandwidth, the higher input resistance of the FET is advantageous.
FETs are divided into two families: junction FET (JFET) and insulated gate FET (IGFET). The IGFET is more commonly known as a metal–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 a p–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 tube triode which, similarly, forms a diode between its grid and cathode. Also, both devices operate in the depletion-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 the reverse biased p–n junction is replaced by a metal–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 into depletion-mode and enhancement-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 can "enhance" the conduction. For the depletion mode, the channel is on at zero bias, and a gate potential (of the opposite polarity) can "deplete" 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),<ref name="computer history-transistor"/> is a type of field-effect transistor that is fabricated by the controlled oxidation of a semiconductor, typically silicon. It has an insulated gate, 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 electronic signals. The MOSFET is by far the most common transistor, and the basic building block of most modern electronics.<ref name="triumph"/> The MOSFET accounts for 99.9% of all transistors in the world.<ref name="computerhistory2018">"13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". Computer History Museum. April 2, 2018. Retrieved July 28, 2019.</ref>
Bipolar transistors are so named because they conduct by using both majority and minority carriers. 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 two p–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—an emitter, a base, and a collector. They are useful in amplifiers because the currents at the emitter and collector are controllable by a relatively small base current.<ref name=Streetman>Streetman, Ben (1992). Solid State Electronic Devices. Englewood Cliffs, NJ: Prentice-Hall. pp. 301–305. ISBN978-0-13-822023-5.</ref> In an n–p–n transistor operating in the active region, the emitter-base junction is forward-biased (electrons and holes 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.<ref name=Streetman/> 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 the Shockley diode model and the Ebers-Moll model. Because of this exponential relationship, the BJT has a higher transconductance 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 called phototransistors.
Usage of MOSFETs and BJTs
The MOSFET is by far the most widely used transistor for both digital circuits as well as analog circuits,<ref>"MOSFET DIFFERENTIAL AMPLIFIER"(PDF). Boston University. Retrieved August 10, 2019.</ref> accounting for 99.9% of all transistors in the world.<ref name="computerhistory2018"/> The bipolar 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 as power MOSFETs, LDMOS and RF CMOS) replaced them for most power electronic applications in the 1980s. In integrated 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 in LCD and OLED displays, types include amorphous silicon, LTPS, LTPO and IGZO transistors
A Darlington 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 in large-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. The ASEA Brown Boveri (ABB) 5SNA2400E170100 ,<ref>"IGBT Module 5SNA 2400E170100"(PDF). Archived from the original(PDF) on April 26, 2012. Retrieved June 30, 2012.</ref> 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 in cascode topology. It was introduced by STMicroelectronics in the 2000s,<ref>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.</ref> and abandoned a few years later around 2012.<ref>STMicroelectronics. "ESBTs". www.st.com. Retrieved February 17, 2019. ST no longer offers these components, this web page is empty, and datasheets are obsoletes</ref>
Multiple-base transistor, used to amplify very-low-level signals in noisy environments such as the pickup of a record player or radio 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 only stochastically.<ref>Zhong Yuan Chang, Willy M. C. Sansen, Low-Noise Wide-Band Amplifiers in Bipolar and CMOS Technologies, page 31, Springer, 1991 ISBN0792390962.</ref>
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 (terminals Base1 and Base2). 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.<ref>"Single Electron Transistors". Snow.stanford.edu. Archived from the original on April 26, 2012. Retrieved June 30, 2012.</ref>
Junctionless nanowire transistor (JNT), uses a simple nanowire of silicon surrounded by an electrically isolated "wedding 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.<ref>"The return of the vacuum tube?". Gizmag.com. May 28, 2012. Archived from the original on April 14, 2016. Retrieved May 1, 2016.</ref>
Super-lattice castellated field effect transistors<ref>Staff, The SE (February 23, 2024). "Chip Industry Week In Review". Semiconductor Engineering.</ref>
Device identification
Three major identification standards are used for designating transistor devices. In each, the alphanumeric prefix provides clues to the type of the device.
Joint Electron Device Engineering Council (JEDEC)
The JEDEC part numbering scheme evolved in the 1960s in the United States. The JEDEC EIA-370 transistor device numbers usually start with 2N, indicating a three-terminal device. Dual-gate field-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.
four-terminal device, such as dual-gate field-effect transistors
Japanese Industrial Standard (JIS)
In Japan, the JIS semiconductor designation (|JIS-C-7012), labels transistor devices starting with 2S,<ref>"Transistor Data". Clivetec.0catch.com. Archived from the original on April 26, 2016. Retrieved May 1, 2016.</ref> e.g., 2SD965, but sometimes the "2S" prefix is not marked on the package–a 2SD965 might only be marked D965 and a 2SC1815 might be listed by a supplier as simply C1815. This series sometimes has suffixes, such as R, O, BL, standing for red, orange, blue, etc., to denote variants, such as tighter hFE (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 from Pro 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 high hFE, such as in: BC549C<ref>"Datasheet for BC549, with A, B and C gain groupings"(PDF). Fairchild Semiconductor. Archived(PDF) from the original on April 7, 2012. Retrieved June 30, 2012.</ref>) or other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A<ref>"Datasheet for BUK854-800A (800volt IGBT)"(PDF). Archived(PDF) from the original on April 15, 2012. Retrieved June 30, 2012.</ref>). The more common prefixes are:
Manufacturers of devices may have their proprietary numbering system, for example CK722. Since devices are second-sourced, a manufacturer's prefix (like "MPF" in MPF102, which originally would denote a MotorolaFET) 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 (possibly Fairchild 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 with "house 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<ref>"Richard Freeman's HP Part numbers Crossreference". Hpmuseum.org. Archived from the original on June 5, 2012. Retrieved June 30, 2012.</ref><ref>"Transistor–Diode Cross Reference – H.P. Part Numbers to JEDEC (pdf)"(PDF). Archived(PDF) from the original on May 8, 2016. Retrieved May 1, 2016.</ref> which is also assigned the CV number: CV7763<ref>"CV Device Cross-reference by Andy Lake". Qsl.net. Archived from the original on January 21, 2012. Retrieved June 30, 2012.</ref>
Naming problems
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-power JFET, the other the higher-powered MOSFET 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 in pinout 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 from germanium (Ge). Silicon (Si) types currently predominate but certain advanced microwave and high-performance versions now employ the compound semiconductor material gallium arsenide (GaAs) and the semiconductor alloysilicon-germanium (SiGe). Single-element semiconductor material (Ge and Si) is described as elemental.
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.
The junction 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.<ref name=Sedra>Sedra, A.S. & Smith, K.C. (2004). Microelectronic circuits (Fifth ed.). New York: Oxford University Press. p. 397 and Figure 5.17. ISBN978-0-19-514251-8.</ref> 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.
The electron mobility and hole mobility columns show the average speed that electrons and holes diffuse through the semiconductor material with an electric 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 bipolar n–p–n transistor tends to be swifter than an equivalent p–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, the high-electron-mobility transistor (HEMT), has a heterostructure (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 on gallium nitride and aluminum gallium nitride (AlGaN/GaN HEMTs) provide still higher electron mobility and are being developed for various applications.
Maximum junction 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 a Schottky diode. This is included in the table because some silicon power IGFETs have a parasitic 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 different semiconductor packages (see image). The two main categories are through-hole (or leaded), and surface-mount, also known as surface-mount device (SMD). The ball 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 to heat 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-mount microwave 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.<ref name="Greig">Greig, William (April 24, 2007). Integrated Circuit Packaging, Assembly and Interconnections. Springer. p. 63. ISBN9780387339139. A hybrid circuit is defined as an assembly containing both active semiconductor devices (packaged and unpackaged)</ref> The IBM 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 include direct chip attach (DCA) and chip-on-board (COB).<ref name="Greig"/>
Amos SW, James MR (1999). Principles of Transistor Circuits. Butterworth-Heinemann. ISBN978-0-7506-4427-3.
Riordan, Michael & Hoddeson, Lillian (1998). Crystal Fire. W.W Norton & Company Limited. ISBN978-0-393-31851-7. The invention of the transistor & the birth of the information age
Warnes, Lionel (1998). Analogue and Digital Electronics. Macmillan Press Ltd. ISBN978-0-333-65820-8.
The Power Transistor - Temperature and Heat Transfer; 1st Ed; John McWane, Dana Roberts, Malcom Smith; McGraw-Hill; 82 pages; 1975; ISBN978-0-07-001729-0. (archive)
Transistor Circuit Analysis - Theory and Solutions to 235 Problems; 2nd Ed; Alfred Gronner; Simon and Schuster; 244 pages; 1970. (archive)
Transistor Physics and Circuits; R.L. Riddle and M.P. Ristenbatt; Prentice-Hall; 1957.
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