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upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electrical power, power. The transistor is one of the basic building blocks of modern
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
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 are found embedded in
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s. Austro-Hungarian
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...
Julius Edgar Lilienfeld proposed the concept of a
field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
in 1926, but it was not possible to actually construct a working device at that time. The first working device to be built was a point-contact transistor invented in 1947 by American physicists John Bardeen and Walter Brattain while working under William Shockley at
Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mul ...
. The three shared the 1956
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
for their achievement. The most widely used type of transistor is the metal–oxide–semiconductor field-effect transistor (MOSFET), which was invented by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959. Transistors revolutionized the field of electronics, and paved the way for smaller and cheaper
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a tr ...
s,
calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
s, and
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
s, among other things. Most transistors are made from very pure
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
, and some from
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...
, 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 A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...
, 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. Many types of transistors are made to standardized specifications by multiple manufacturers.


History

The thermionic triode, a
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...
invented in 1907, enabled amplified
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a tr ...
technology and long-distance
telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...
. The triode, however, was a fragile device that consumed a substantial amount of power. In 1909,
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...
William Eccles discovered the crystal diode oscillator. Austro-Hungarian physicist Julius Edgar Lilienfeld filed a patent for a
field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
(FET) in Canada in 1925, which was intended to be a
solid-state Solid state, or solid matter, is one of the four fundamental states of matter. Solid state may also refer to: Electronics * Solid-state electronics, circuits built of solid materials * Solid state ionics, study of ionic conductors and their ...
replacement for the triode. Lilienfeld also filed identical patents in the United States in 1926 and 1928. However, Lilienfeld 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-quality
semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
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. In 1934, German inventor Oskar Heil patented a similar device in Europe.


Bipolar transistors

From November 17, 1947, to December 23, 1947, John Bardeen and Walter Brattain at
AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile ...
's
Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mul ...
in Murray Hill, New Jersey, performed experiments and observed that when two gold point contacts were applied to a crystal of
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...
, a signal was produced with the output power greater than the input. 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''. According to Lillian Hoddeson and Vicki Daitch, Shockley had 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. In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
"for their researches on semiconductors and their discovery of the transistor effect". Shockley's research 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 the surface states, the dangling bond, and the
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...
and
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
compound materials. In the course of trying to understand the mysterious reasons behind their failure to build a working FET, this led them instead to invent the bipolar point-contact and junction transistors. In 1948, the point-contact transistor was independently invented by German physicists Herbert Mataré and
Heinrich Welker Heinrich Johann Welker (9 September 1912 in Ingolstadt – 25 December 1981 in Erlangen) was a German theoretical and applied physicist who invented the "transistron", a transistor made at Westinghouse independently of the first successful trans ...
while working at the '' Compagnie des Freins et Signaux Westinghouse'', a Westinghouse subsidiary located in
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
. Mataré had previous experience in developing crystal rectifiers from
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
and germanium in the German
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...
effort during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. Using this knowledge, he began researching the phenomenon of "interference" in 1947. By June 1948, witnessing currents flowing through point-contacts, Mataré 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 before them, the company rushed to get its "transition" into production for amplified use in France's telephone network and filed his first transistor patent application on August 13, 1948. The first bipolar junction transistors were invented by Bell Labs' William Shockley, which applied for patent (2,569,347) on June 26, 1948. On April 12, 1950, Bell Labs chemists
Gordon Teal Gordon Kidd Teal (January 10, 1907 – January 7, 2003) was an American engineer. He invented a method of applying the Czochralski method to produce extremely pure germanium single crystals used in making greatly improved transistors.
and Morgan Sparks had successfully produced a working bipolar NPN junction amplifying germanium transistor. Bell Labs had announced the discovery of this new "sandwich" transistor in a press release on July 4, 1951. The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating at frequencies up to . These 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. AT&T first used transistors in telecommunications equipment in circuits of the No. 4A Toll Crossbar Switching System in 1953 for selecting trunk circuits from routing information encoded on translator cards. 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'' between August 29, 1953 and September 6, 1953. The first "production" pocket transistor radio was the
Regency TR-1 The Regency TR-1 was the first commercially manufactured transistor radio, introduced in 1954. Despite mediocre performance, about 150,000 units were sold, due to the novelty of its small size and portability. Previously, transistors had only bee ...
, released in October 1954. Produced as a joint venture between the Regency Division of Industrial Development Engineering Associates, I.D.E.A. and
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...
of Dallas Texas, the TR-1 was manufactured in Indianapolis, Indiana. It was a near pocket-sized radio featuring 4 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 different colours: black, ivory, mandarin red, cloud grey, mahogany and olive green. Other colours were to shortly follow. The first "production" all-transistor car radio was developed by Chrysler and Philco corporations and it was announced in the April 28, 1955 edition of the Wall Street Journal. Chrysler had made the all-transistor car radio, Mopar model 914HR, available as an option starting in fall 1955 for its new line of 1956 Chrysler and Imperial cars which first hit the dealership showroom floors on October 21, 1955. The
Sony , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...
TR-63, released in 1957, was the first mass-produced transistor radio, leading to the mass-market penetration of transistor radios. The TR-63 went on to sell seven million units worldwide by the mid-1960s. Sony's success with transistor radios led to transistors replacing vacuum tubes as the dominant
electronic technology The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplificatio ...
in the late 1950s. The first working silicon transistor was developed at Bell Labs on January 26, 1954, by
Morris Tanenbaum Morris Tanenbaum (November 10, 1928 - February 26, 2023) was an American physical chemist and executive who worked at Bell Laboratories and AT&T Corporation. Tanenbaum made significant contributions in the fields of transistor development and ...
. The first commercial silicon transistor was produced by
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...
in 1954. This was the work of
Gordon Teal Gordon Kidd Teal (January 10, 1907 – January 7, 2003) was an American engineer. He invented a method of applying the Czochralski method to produce extremely pure germanium single crystals used in making greatly improved transistors.
, an expert in growing crystals of high purity, who had previously worked at Bell Labs.


Field effect transistors

The basic principle of the
field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
(FET) was first proposed by Austrian physicist Julius Edgar Lilienfeld in 1926, when he filed a
patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...
for a device similar to MESFET and in 1928 when he filed a patent for an insulated-gate field-effect transistor. The FET concept was later also theorized by German engineer Oskar Heil in the 1930s and by William Shockley in the 1940s. In 1945
JFET The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifi ...
was patented by
Heinrich Welker Heinrich Johann Welker (9 September 1912 in Ingolstadt – 25 December 1981 in Erlangen) was a German theoretical and applied physicist who invented the "transistron", a transistor made at Westinghouse independently of the first successful trans ...
. 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. In 1948 Bardeen patented the progenitor of MOSFET, an insulated-gate FET (IGFET) with an inversion layer. Bardeen's patent as well as the concept of an inversion layer forms the basis of CMOS technology today.


MOSFET (MOS transistor)

Semiconductor companies initially focused on junction transistors in the early years of the semiconductor industry. The junction transistor was a relatively bulky device that was difficult to mass-produce, which limited it to several specialized applications.
Field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
s (FETs) were theorized as potential alternatives to junction transistors, but researchers initially could not get FETs to work properly, largely due to the troublesome surface state barrier that prevented the external electric field from penetrating the material. In the 1950s, Egyptian engineer Mohamed Atalla investigated the surface properties of
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
semiconductors at Bell Labs, where he proposed a new method of
semiconductor device fabrication Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuit (IC) chips such as modern computer processors, microcontrollers, and memory chips such as NAND flash and DRAM that are ...
, coating a silicon wafer with an insulating layer of
silicon oxide Silicon oxide may refer to either of the following: * Silicon dioxide or quartz, SiO2, very well characterized *Silicon monoxide Silicon monoxide is the chemical compound with the formula SiO where silicon is present in the oxidation state +2. In ...
so that electricity could reliably penetrate to the conducting silicon below, overcoming the surface states that prevented electricity from reaching the semiconducting layer. This is known as surface passivation, a method that became critical to the semiconductor industry as it later made possible the mass-production of silicon
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s. He presented his findings in 1957. Building on his surface passivation method, he developed the metal–oxide–semiconductor (MOS) process. He proposed the MOS process could be used to build the first working silicon FET, which he began working on building with the help of his Korean colleague Dawon Kahng. The metal–oxide–semiconductor field-effect transistor (MOSFET), or ''MOS transistor'', was invented by Mohamed Atalla and Dawon Kahng in 1959. The MOSFET was the first truly compact transistor that could be miniaturized and mass-produced for a wide range of uses. In a self-aligned
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
process, a transistor is formed wherever the gate layer (polysilicon or metal) crosses a diffusion layer. Mead, Carver A.; Conway, Lynn (1980) ''
Introduction to VLSI Systems Introduction, The Introduction, Intro, or The Intro may refer to: General use * Introduction (music), an opening section of a piece of music * Introduction (writing), a beginning section to a book, article or essay which states its purpose and ...
'' Reading, Mass.: Addison-Wesley: ISBN 2-201-04358-0
With its high scalability, and much lower power consumption and higher density than bipolar junction transistors, the MOSFET made it possible to build high-density integrated circuits, allowing the integration of more than 10,000 transistors in a single IC.
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
(complementary
MOS MOS or Mos may refer to: Technology * MOSFET (metal–oxide–semiconductor field-effect transistor), also known as the MOS transistor * Mathematical Optimization Society * Model output statistics, a weather-forecasting technique * MOS (fil ...
) was invented by
Chih-Tang Sah Chih-Tang "Tom" Sah (; born in November 1932 in Beijing, China) is a Chinese-American electronics engineer and condensed matter physicist. He is best known for inventing CMOS (complementary MOS) logic with Frank Wanlass at Fairchild Semiconducto ...
and Frank Wanlass at Fairchild Semiconductor in 1963. The first report of a floating-gate MOSFET was made by Dawon Kahng and Simon Sze in 1967. A double-gate MOSFET was first demonstrated in 1984 by Electrotechnical Laboratory researchers Toshihiro Sekigawa and Yutaka Hayashi.
FinFET A fin field-effect transistor (FinFET) is a multigate device, a MOSFET (metal-oxide-semiconductor field-effect transistor) built on a substrate where the gate is placed on two, three, or four sides of the channel or wrapped around the channel, ...
(fin field-effect transistor), a type of 3D non-planar
multi-gate A multigate device, multi-gate MOSFET or multi-gate field-effect transistor (MuGFET) refers to a metal–oxide–semiconductor field-effect transistor (MOSFET) that has more than one gate on a single transistor. The multiple gates may be control ...
MOSFET, originated from the research of Digh Hisamoto and his team at Hitachi Central Research Laboratory in 1989.


Importance

Transistors are the key active components in practically all modern
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
. Many thus consider the transistor to be one of the greatest inventions of the 20th century. The invention of the first transistor at Bell Labs was named an IEEE Milestone in 2009. The list of IEEE Milestones also includes the inventions of the junction transistor in 1948 and the MOSFET in 1959. The
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
(metal–oxide–semiconductor field-effect transistor), also known as the MOS transistor, is by far the most widely used transistor, used in applications ranging from
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
s and
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
to communications technology such as
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whi ...
s. The MOSFET has been considered to be the most important transistor, possibly the most important invention in electronics, and the birth of modern electronics. The MOS transistor has been the fundamental building block of modern
digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usu ...
since the late 20th century, paving the way for the digital age. The
US Patent and Trademark Office The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that serves as the national patent office and trademark registration authority for the United States. The USPTO's headquarters are in Alexa ...
calls it a "groundbreaking invention that transformed life and culture around the world". Its importance in today's
society A society is a group of individuals involved in persistent social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same political authority and dominant cultural expectations. Soc ...
rests on its ability to be mass-produced using a highly automated process (
semiconductor device fabrication Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuit (IC) chips such as modern computer processors, microcontrollers, and memory chips such as NAND flash and DRAM that are ...
) that achieves astonishingly low per-transistor costs. MOSFETs are the most numerously produced artificial objects ever with more than 13 sextillion manufactured by 2018. Although several companies each produce over a billion individually packaged (known as '' discrete'') MOS transistors every year, the vast majority of transistors are now produced in
integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tin ...
(often shortened to ''IC'', ''microchips'' or simply ''chips''), along with
diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diod ...
s,
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...
s,
capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...
s and other
electronic component An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are no ...
s, to produce complete electronic circuits. A
logic gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...
consists of up to about twenty transistors whereas an advanced
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...
, as of 2022, can use as many as 57 billion transistors (
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
s). The transistor's low cost, flexibility, and reliability have made it a ubiquitous device. 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 A computer program is a sequence or set of instructions in a programming language for a computer to Execution (computing), execute. Computer programs are one component of software, which also includes software documentation, documentation and oth ...
to carry out a control function than to design an equivalent mechanical system to control that same function.


Simplified operation

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. This property is called
gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...
. It can produce a stronger output signal, a voltage or current, which is proportional to a weaker input signal and thus, it can act as an
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch, where the amount of current is determined by other circuit elements. There are two types of transistors, which have slight differences in how they are used in a circuit. A '' bipolar transistor'' has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For a ''
field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
'', the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain. The image represents a typical bipolar transistor in a circuit. A charge will flow between emitter and collector terminals depending on the current in the base. Because internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The amount of this voltage depends on the material the transistor is made from and is referred to as ''V''BE.


Transistor as a switch

Transistors are commonly used in
digital circuit In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathemati ...
s 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 gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...
s. Important parameters for this application include the current switched, the voltage handled, and the switching speed, characterized by the rise and fall times. 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. 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''. 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. The base resistor value is calculated from the supply voltage, transistor C-E junction voltage drop, collector current, and amplification factor beta.


Transistor as an amplifier

The common-emitter amplifier is designed so that a small change in voltage (''V''in) 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 ''V''in produce large changes in ''V''out. Various configurations of single transistor amplifiers are possible, with some providing current gain, some voltage gain, and some both. From
mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whi ...
s to
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertising, ...
s, vast numbers of products include amplifiers for
sound reproduction Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording ...
, radio transmission, and
signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
. 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. Modern transistor audio amplifiers of up to a few hundred
watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
s 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 An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
. * 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 Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two electrically charged objects caused by contact, an electrical short or dielectric breakdown. A buildup of static electricity can be caused by tribochar ...
in handling. Vacuum tubes are electrically much more rugged. * They are sensitive to radiation and
cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
s (special radiation-hardened chips are used for spacecraft devices). * 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.


Types


Classification

, - style="text-align:center;" , , , PNP, , , , P-channel , - style="text-align:center;" , , , NPN, , , , N-channel , - style="text-align:center;" , BJT, , , , JFET, , , - style="text-align:center;" , , , , , , , P-channel , - style="text-align:center;" , , , , , , , N-channel , - style="text-align:center;" , colspan="2", MOSFET enh, , MOSFET dep, , Transistors are categorized by * Structure:
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
(IGFET), BJT,
JFET The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifi ...
, insulated-gate bipolar transistor (IGBT), other types. * Semiconductor material (
dopant A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. Whe ...
s): ** The metalloids;
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...
(first used in 1947) and
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
(first used in 1954)—in amorphous, polycrystalline and monocrystalline form. ** The compounds
gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated c ...
(1966) and silicon carbide (1997). ** The
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
silicon-germanium (1989) ** The allotrope of carbon
graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.
(research ongoing since 2004), etc. (see #Semiconductor material, Semiconductor material). * Electrical polarity (positive and negative): NPN, PNP (BJTs), N-channel, P-channel (FETs). * Maximum power rating: low, medium, high. * Maximum operating frequency: low, medium, high,
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a tr ...
(RF),
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
frequency (the maximum effective frequency of a transistor in a common-emitter or common-source circuit is denoted by the term , an abbreviation for transition frequency—the frequency of transition is the frequency at which the transistor yields unity voltage gain) * Application: switch, general purpose, audio,
high voltage High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant sp ...
, super-beta, matched pair. * Physical packaging:
through-hole In electronics, through-hole technology (also spelled "thru-hole") is a manufacturing scheme in which leads on the components are inserted through holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side, either ...
metal, through-hole plastic,
surface mount Surface-mount technology (SMT), originally called planar mounting, is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). An electrical component mounted in this manner is referred ...
, ball grid array, power modules (see Packaging). * Amplification factor , ( transistor beta) or ( transconductance). * Working temperature: Extreme temperature transistors and traditional temperature transistors (). Extreme temperature transistors include high-temperature transistors (above ) and low-temperature transistors (below ). The high-temperature transistors that operate thermally stable up to can be developed by a general strategy of blending interpenetrating semi-crystalline conjugated polymers and high glass-transition temperature insulating polymers. Hence, a particular transistor may be described as ''silicon, surface-mount, BJT, NPN, low-power, high-frequency switch''.


Mnemonics

Convenient
mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and image ...
to remember the type of transistor (represented by a 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 iN Proudly". This however 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).


Field-effect transistor (FET)

The ''
field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
'', 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 () is increased, the drain–source current () increases exponentially for below threshold, and then at a roughly quadratic rate: (, where is the threshold voltage at which drain current begins) in the " space-charge-limited" region above threshold. A quadratic behavior is not observed in modern devices, for example, at the
65 nm The 65  nm process is an advanced lithographic node used in volume CMOS (MOSFET) semiconductor fabrication. Printed linewidths (i.e. transistor gate lengths) can reach as low as 25 nm on a nominally 65 nm process, while the pitch ...
technology node. For low noise at narrow bandwidth, the higher input resistance of the FET is advantageous. FETs are divided into two families: ''junction FET'' (
JFET The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifi ...
) and ''insulated gate FET'' (IGFET). The IGFET is more commonly known as a ''metal–oxide–semiconductor FET'' (
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
), 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 A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
. 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.


Metal–oxide–semiconductor FET (MOSFET)

The metal-oxide-semiconductor field-effect transistor (
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of field-effect transistor that is fabricated by the controlled oxidation of a semiconductor, typically
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
. 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 The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
. The MOSFET accounts for 99.9% of all transistors in the world.


Bipolar junction transistor (BJT)

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 junction A p–n junction is a boundary or interface between two types of semiconductor materials, p-type and n-type, inside a single crystal of semiconductor. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contai ...
s: 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
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
s because the currents at the emitter and collector are controllable by a relatively small base current. In an n–p–n transistor operating in the active region, the emitter-base junction is forward biased (
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...
s 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. 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 (''V''BE) is increased the base-emitter current and hence the collector-emitter current (''I''CE) increase exponentially according to the Shockley diode model and the
Ebers-Moll model A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
. 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 The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
is by far the most widely used transistor for both
digital circuit In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathemati ...
s as well as analog circuits, accounting for 99.9% of all transistors in the world. 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 LDMOS (laterally-diffused metal-oxide semiconductor) is a planar double-diffused MOSFET (metal–oxide–semiconductor field-effect transistor) used in amplifiers, including microwave power amplifiers, RF power amplifiers and audio power amplifi ...
and RF CMOS) replaced them for most power electronic applications in the 1980s. In
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s, 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.


Other transistor types

*
Field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
(FET): ** Metal–oxide–semiconductor field-effect transistor (MOSFET), where the gate is insulated by a shallow layer of insulator *** p-type MOS (PMOS) *** n-type MOS (NMOS) *** complementary MOS (CMOS) **** RF CMOS, for power electronics ***
Multi-gate field-effect transistor A multigate device, multi-gate MOSFET or multi-gate field-effect transistor (MuGFET) refers to a metal–oxide–semiconductor field-effect transistor (MOSFET) that has more than one gate on a single transistor. The multiple gates may be contr ...
(MuGFET) ****
Fin field-effect transistor A fin field-effect transistor (FinFET) is a multigate device, a MOSFET (metal-oxide-semiconductor field-effect transistor) built on a substrate where the gate is placed on two, three, or four sides of the channel or wrapped around the channel, f ...
(FinFET), source/drain region shapes fins on the silicon surface ****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 nanosheets instead of nanowires, made by Samsung *** Thin-film transistor, used in LCD and OLED displays *** Floating-gate MOSFET (FGMOS), for non-volatile storage *** Power MOSFET, for power electronics **** lateral diffused MOS (LDMOS) **
Carbon nanotube field-effect transistor A carbon nanotube field-effect transistor (CNTFET) is a field-effect transistor that utilizes a single carbon nanotube or an array of carbon nanotubes as the channel material instead of bulk silicon in the traditional MOSFET structure. First demons ...
(CNFET), where the channel material is replaced by a carbon nanotube **
Junction gate field-effect transistor The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifiers. ...
(JFET), where the gate is insulated by a reverse-biased p–n junction ** Metal–semiconductor field-effect transistor (MESFET), similar to JFET with a Schottky junction instead of a p–n junction *** High-electron-mobility transistor (HEMT) **
Inverted-T field-effect transistor The inverted-T field-effect transistor (ITFET) is a type of field effect transistor invented by Leo Mathew at Freescale Semiconductor Freescale Semiconductor, Inc. was an American semiconductor manufacturer. It was created by the divestiture ...
(ITFET) ** Fast-reverse epitaxial diode field-effect transistor (FREDFET) ** Organic field-effect transistor (OFET), in which the semiconductor is an organic compound ** Ballistic transistor (disambiguation) ** FETs used to sense the environment *** Ion-sensitive field-effect transistor (ISFET), to measure ion concentrations in solution, *** Electrolyte–oxide–semiconductor field-effect transistor (EOSFET),
neurochip A neurochip is an integrated circuit chip (such as a microprocessor) that is designed for interaction with neuronal cells. Formation It is made of silicon that is doped in such a way that it contains EOSFETs (electrolyte- oxide-semiconducto ...
, *** Deoxyribonucleic acid field-effect transistor (DNAFET). * Bipolar junction transistor (BJT): ** Heterojunction bipolar transistor, up to several hundred GHz, common in modern ultrafast and RF circuits ** Schottky transistor ** avalanche transistor ** 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'' , 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 ** Phototransistor. ** Emitter-switched bipolar transistor (ESBT) is a monolithic configuration of a high-voltage bipolar transistor and a low-voltage power MOSFET in
cascode The cascode is a two-stage amplifier that consists of a common-emitter stage feeding into a common-base stage. Compared to a single amplifier stage, this combination may have one or more of the following characteristics: higher input–outpu ...
topology. It was introduced by STMicroelectronics in the 2000s, and abandoned a few years later around 2012. **
Multiple-emitter transistor A multiple-emitter transistor is a specialized bipolar transistor mostly used at the inputs of integrated circuit TTL NAND logic gates. Input signals are applied to the emitters. The voltage presented to the following stage is pulled low if any o ...
, used in
transistor–transistor logic Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as o ...
and integrated current mirrors ** 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
stochastic Stochastic (, ) refers to the property of being well described by a random probability distribution. Although stochasticity and randomness are distinct in that the former refers to a modeling approach and the latter refers to phenomena themselv ...
ally. *
Tunnel field-effect transistor The tunnel field-effect transistor (TFET) is an experimental type of transistor. Even though its structure is very similar to a metal-oxide-semiconductor field-effect transistor (MOSFET), the fundamental switching mechanism differs, making this devi ...
, where it switches by modulating quantum tunneling through a barrier. * Diffusion transistor, formed by diffusing dopants into semiconductor substrate; can be both BJT and FET. *
Unijunction transistor A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier. It is used in free-running oscillators, ...
, can be used as simple pulse generators. 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 transistor A single-electron transistor (SET) is a sensitive electronic device based on the Coulomb blockade effect. In this device the electrons flow through a tunnel junction between source/drain to a quantum dot (conductive island). Moreover, the electric ...
s (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. *
Nanofluidic transistor Nanofluidic circuitry is a nanotechnology aiming for control of fluids in nanometer scale. Due to the effect of an electrical double layer within the fluid channel, the behavior of nanofluid is observed to be significantly different compared wit ...
, controls the movement of ions through sub-microscopic, water-filled channels. * Multigate devices: ** Tetrode transistor **
Pentode transistor A pentode transistor is any transistor having five active terminals. Early pentode transistors One early pentode transistor was developed in the early 1950s as an improvement over the point-contact transistor. *A point-contact transistor having thr ...
** Trigate transistor (prototype by Intel) **
Dual-gate field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which ...
s have a single channel with two gates in
cascode The cascode is a two-stage amplifier that consists of a common-emitter stage feeding into a common-base stage. Compared to a single amplifier stage, this combination may have one or more of the following characteristics: higher input–outpu ...
, a configuration optimized for ''high-frequency amplifiers'', ''mixers'', and
oscillators Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
. * 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. * 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. *
Organic electrochemical transistor The organic electrochemical transistor (OECT) is an organic electronic device which functions like a transistor. The current flowing through the device is controlled by the exchange of ions between an electrolyte and the OECT channel composed of an ...
. * Solaristor (from solar cell transistor), a two-terminal gate-less self-powered phototransistor.


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 The JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States. JEDEC has over 300 members, including some of the w ...
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 transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs co ...
s 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.


Japanese Industrial Standard (JIS)

In Japan, the JIS semiconductor designation (, JIS-C-7012), labels transistor devices starting with ''2S'', 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 ''h''FE (gain) groupings.


European Electronic Component Manufacturers Association (EECA)

The European Electronic Component Manufacturers Association (EECA) uses a numbering scheme that was inherited from
Pro Electron Pro Electron or EECA is the European type designation and registration system for active components (such as semiconductors, liquid crystal displays, sensor devices, electronic tubes and cathode ray tubes). Pro Electron was set up in 1966 in Br ...
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 ''h''FE, such as in: BC549C) or other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A). The more common prefixes are:


Proprietary

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
Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorola ...
FET) 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). Military part numbers sometimes are assigned their codes, such as the British Military CV Naming System. 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 which is also assigned the CV number: CV7763


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 junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifi ...
, the other the higher-powered
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
2SJ176). As older "through-hole" transistors are given
surface-mount Surface-mount technology (SMT), originally called planar mounting, is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). An electrical component mounted in this manner is referre ...
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.


Construction


Semiconductor material

The first BJTs were made from
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...
(Ge).
Silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
(Si) types currently predominate but certain advanced microwave and high-performance versions now employ the ''compound semiconductor'' material
gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated c ...
(GaAs) and the ''semiconductor alloy'' silicon-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. 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: # Its maximum temperature is limited. # It has relatively high leakage current. # It cannot withstand high voltages. # 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 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 Aluminium gallium nitride (AlGaN) is a semiconductor material. It is any alloy of aluminium nitride and gallium nitride. The bandgap of AlxGa1−xN can be tailored from 3.4eV (xAl=0) to 6.2eV (xAl=1). AlGaN is used to manufacture light-emitting d ...
(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 The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage ...
. 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.


Packaging

Discrete transistors can be individually packaged transistors or unpackaged transistor chips (dies). Transistors come in many different semiconductor packages (see image). The two main categories are ''
through-hole In electronics, through-hole technology (also spelled "thru-hole") is a manufacturing scheme in which leads on the components are inserted through holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side, either ...
'' (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 sink A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, ...
s 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 shortlist 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. 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).


Flexible transistors

Researchers have made several kinds of flexible transistors, including organic field-effect transistors. Flexible transistors are useful in some kinds of flexible displays and other flexible electronics.


See also

* Band gap *
Digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usu ...
*
Diffused junction transistor A diffused junction transistor is a transistor formed by diffusing dopants into a semiconductor substrate. The diffusion process was developed later than the alloy junction and grown junction processes for making bipolar junction transistors ( ...
* Moore's law * Optical transistor * Semiconductor device modeling * Transistor count *
Transistor model Transistors are simple devices with complicated behavior. In order to ensure the reliable operation of circuits employing transistors, it is necessary to scientifically model the physical phenomena observed in their operation using transistor mod ...
* Transresistance * Very Large Scale Integration *
Trancitor The trancitor as the combined word of a "transfer-capacitor" is to be considered as another active-device category besides the transistor as a "transfer-resistor". As observed in the table shown, four kinds of active devices are theoretically de ...


References


Further reading

;Books * * * The invention of the transistor & the birth of the information age * * ''The Power Transistor - Temperature and Heat Transfer''; 1st Ed; John McWane, Dana Roberts, Malcom Smith; McGraw-Hill; 82 pages; 1975; . (archive)
/small> * ''Transistor Circuit Analysis - Theory and Solutions to 235 Problems''; 2nd Ed; Alfred Gronner; Simon and Schuster; 244 pages; 1970. (archive)
/small> * ''Transistor Physics and Circuits''; R.L. Riddle and M.P. Ristenbatt; Prentice-Hall; 1957. ;Periodicals * * * ;Databooks
Discrete Databook
1985; Fairchild (now ON Semiconductor)
Small-Signal Semiconductors Databook
1987; Motorola (now ON semiconductor)
Discrete Power Devices Databook
1982; SGS (now STMicroelectronics)
Discrete Databook
1978; National Semiconductor (now Texas Instruments)


External links


BBC: Building the digital age
photo history of transistors


''IEEE Global History Network, The Transistor and Portable Electronics''
All about the history of transistors and integrated circuits.
''This Month in Physics History: November 17 to December 23, 1947: Invention of the First Transistor''
From the
American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...

''50 Years of the Transistor''
From Science Friday, December 12, 1997 ; Pinouts
Common transistor pinouts
{{Authority control 1947 in computing 1947 in technology 20th-century inventions American inventions Bell Labs Computer-related introductions in 1947 Electrical components Hungarian inventions Semiconductor devices