Transistor

Transistor

Overview
A transistor is a semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 device
Semiconductor device
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications...

 used to amplify
Electronic amplifier
An electronic amplifier is a device for increasing the power of a signal.It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude...

 and switch electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...

 can be much more than the controlling (input) power, a transistor can amplify
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...

 a signal.
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Unanswered Questions
Encyclopedia
A transistor is a semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 device
Semiconductor device
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications...

 used to amplify
Electronic amplifier
An electronic amplifier is a device for increasing the power of a signal.It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude...

 and switch electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...

 can be much more than the controlling (input) power, a transistor can amplify
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...

 a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s.

The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its release in the early 1950s the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

s, calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...

s, and computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s, among other things.

History



Physicist Julius Edgar Lilienfeld
Julius Edgar Lilienfeld
Julius Edgar Lilienfeld was an Austro-Hungarian physicist. He was born in Lemberg in Austria-Hungary , moved to the United States in the early 1920s, and became American citizen in 1934...

 filed a patent for a field-effect transistor
Field-effect transistor
The field-effect transistor is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with...

 (FET) in Canada in 1925. 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. Since the production of high-quality semiconductor materials was still decades away, Lilienfeld's solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...

 amplifier ideas would not have found practical use in the 1920s and 1930s, even if such a device were built. In 1934, German inventor Oskar Heil
Oskar Heil
Oskar Heil was a German electrical engineer and inventor. He studied physics, chemistry, mathematics, and music at the Georg-August University of Göttingen and was awarded his PhD in 1933, for his work on molecular spectroscopy.-Personal life:At the Georg-August University in Göttingen, Oskar Heil...

 patented a similar device.

From November 17, 1947 to December 23, 1947, John Bardeen
John Bardeen
John Bardeen was an American physicist and electrical engineer, the only person to have won the Nobel Prize in Physics twice: first in 1956 with William Shockley and Walter Brattain for the invention of the transistor; and again in 1972 with Leon Neil Cooper and John Robert Schrieffer for a...

 and Walter Brattain at AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...

's Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...

 in the United States, performed experiments and observed that when two gold point contacts were applied to a crystal of germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

, a signal was produced with the output power greater than the input. Solid State Physics Group leader William Shockley
William Shockley
William Bradford Shockley Jr. was an American physicist and inventor. Along with John Bardeen and Walter Houser Brattain, Shockley co-invented the transistor, for which all three were awarded the 1956 Nobel Prize in Physics.Shockley's attempts to commercialize a new transistor design in the 1950s...

 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 portmanteau of the term "transfer resistor". According to Lillian Hoddeson and Vicki Daitch, authors of a recent biography of John Bardeen, Shockley had proposed that Bell Lab's 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 since the idea of a field-effect transistor which 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
Point-contact transistor
A point-contact transistor was the first type of solid-state electronic transistor ever constructed. It was made by researchers John Bardeen and Walter Houser Brattain at Bell Laboratories in December 1947. They worked in a group led by physicist William Bradford Shockley...

 with bipolar junction. In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956 Nobel Prize in Physics
Nobel Prize in Physics
The Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and...

 "for their researches on semiconductors and their discovery of the transistor effect."

In 1948, the point-contact transistor was independently invented by German physicists Herbert Mataré
Herbert Mataré
Herbert Franz Mataré was a German physicist. The focus of his research was the field of semiconductor research. His best-known work is the first functional "European" transistor, which he developed and patented together with Heinrich Welker in the vicinity of Paris in 1948, at the same time and...

 and Heinrich Welker
Heinrich Welker
Heinrich Johann Welker was a German theoretical and applied physicist who invented the "transistron", a form of transistor made at Westinghouse independently of the first successful transistor made at Bell Laboratories...

 while working at the Compagnie des Freins et Signaux, a Westinghouse
Westinghouse Electric (1886)
Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...

 subsidiary located in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

. Mataré had previous experience in developing crystal rectifiers from silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 and germanium in the German radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 effort during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Using this knowledge, he began researching the phenomenon of "interference" in 1947. By witnessing currents flowing through point-contacts, similar to what Bardeen and Brattain had accomplished earlier in December 1947, Mataré by June 1948, was able to produce consistent results by using samples of germanium produced by Welker. Realizing that Bell Lab's scientists had already invented the transistor before them, the company rushed to get its "transistron" into production for amplified use in France's telephone network.

The first silicon transistor was produced by Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

 in 1954. This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs. The first MOS
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

 transistor actually built was by Kahng and Atalla at Bell Labs in 1960.

Importance


The transistor is the key active component in practically all modern electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

. Many consider it to be one of the greatest inventions of the 20th century. Its importance in today's society rests on its ability to be mass produced
Mass production
Mass production is the production of large amounts of standardized products, including and especially on assembly lines...

 using a highly automated process (semiconductor device fabrication) that achieves astonishingly low per-transistor costs. The invention of the first transistor at Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...

 was named an IEEE Milestone in 2009.

Although several companies each produce over a billion individually packaged (known as discrete) transistors every year,
the vast majority of transistors now are produced in integrated circuits (often shortened to IC, microchips or simply chips), along with diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

s, resistors, capacitors and other electronic components, to produce complete electronic circuits. A logic gate
Logic gate
A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...

 consists of up to about twenty transistors whereas an advanced microprocessor, as of 2011, can use as many as 3 billion transistors (MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

s).
"About 60 million transistors were built in 2002 ... for [each] man, woman, and child on Earth."

The transistor's low cost, flexibility, and reliability have made it a ubiquitous device. Transistorized mechatronic
Mechatronics
Mechatronics is the combination of mechanical engineering, electronic engineering, computer engineering, software engineering, control engineering, and systems design engineering in order to design, and manufacture useful products. Mechatronics is a multidisciplinary field of engineering, that is...

 circuits have replaced electromechanical devices
Cam timer
A cam timer is an electromechanical system for controlling a sequence of events automatically.-Description:An electric motor drives, through a reduction gearbox, a shaft on which is arranged a series of cams. Associated with each cam is one or more switches. The motor rotates at a fixed speed, and...

 in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...

 and write a computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 to carry out a control function than to design an equivalent mechanical control function.

Simplified operation




The essential usefulness of a transistor comes from its ability to 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
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...

. A transistor can control its output in proportion to the input signal; that is, it can act as an amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...

. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....

, 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 from the base to the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain.

The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Since 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 VBE.

Transistor as a switch


Transistors are commonly used as electronic switches, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates.

In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises the base and collector current rise exponentially, and the collector voltage drops because of the collector load resistor. The relevant equations:
VRC = ICE × RC, the voltage across the load (the lamp with resistance RC)
VRC + VCE = VCC, the supply voltage shown as 6V


If VCE could fall to 0 (perfect closed switch) then Ic could go no higher than VCC / RC, even with higher base voltage and current. The transistor is then said to be saturated. Hence, values of input voltage can be chosen such that the output is either completely off, or completely on. The transistor is acting as a switch, and this type of operation is common in digital circuits where only "on" and "off" values are relevant.

Transistor as an amplifier


The common-emitter amplifier is designed so that a small change in voltage in (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings in Vin produce large changes in Vout.
Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.

From mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

s to television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

s, vast numbers of products include amplifiers for sound reproduction, radio transmission
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...

, and signal processing
Signal processing
Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time...

. 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
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s are common and relatively inexpensive.

Comparison with vacuum tubes


Prior to the development of transistors, vacuum (electron) tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s (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 their vacuum tube predecessors in most applications are
  • Small size and minimal weight, allowing the development of miniaturized electronic devices.
  • Highly automated manufacturing processes, resulting in low per-unit cost.
  • Lower possible operating voltages, making transistors suitable for small, battery-powered applications.
  • No warm-up period for cathode heaters required after power application.
  • Lower power dissipation and generally greater energy efficiency.
  • Higher reliability and greater physical ruggedness.
  • Extremely long life. Some transistorized devices have been in service for more than 50 years.
  • Complementary devices available, facilitating the design of complementary-symmetry circuits, something not possible with vacuum tubes.
  • Insensitivity to mechanical shock and vibration, thus avoiding the problem of microphonics
    Microphonics
    Microphonics describes the phenomenon where certain components in electronic devices transform mechanical vibrations into an undesired electrical signal...

     in audio applications.

Limitations

  • Silicon transistors typically do not operate at voltages higher than about 1000 volts (SiC
    Silicon carbide
    Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...

     devices can be operated as high as 3000 volts). In contrast, vacuum tubes have been developed that can be operated at tens of thousands of volts.
  • High-power, high-frequency operation, such as that used in over-the-air television broadcasting
    Television
    Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

    , is better achieved in vacuum tubes due to improved electron mobility
    Electron mobility
    In solid-state physics, the electron mobility characterizes how quickly an electron can move through a metal or semiconductor, when pulled by an electric field. In semiconductors, there is an analogous quantity for holes, called hole mobility...

     in a vacuum.
  • Silicon transistors are much more vulnerable than vacuum tubes to an electromagnetic pulse
    Electromagnetic pulse
    An electromagnetic pulse is a burst of electromagnetic radiation. The abrupt pulse of electromagnetic radiation usually results from certain types of high energy explosions, especially a nuclear explosion, or from a suddenly fluctuating magnetic field...

     generated by a high-altitude nuclear explosion
    Nuclear explosion
    A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...

    .
  • Silicon transistors when amplifying near the saturation point typically fail and create distortion. Vacuum tubes under the same stress conditions fail more gradually and create a distortion that is more pleasant to the ear.

Types



|- 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;"
|JFET||colspan="2"|MOSFET enh||MOSFET dep
Transistors are categorized by
  • Semiconductor material: graphene
    Graphene
    Graphene is an allotrope of carbon, whose structure is one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The term graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm, who described single-layer...

    , germanium
    Germanium
    Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

    , silicon
    Silicon
    Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

    , gallium arsenide, silicon carbide
    Silicon carbide
    Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...

    , etc.
  • Structure: BJT
    Bipolar junction transistor
    |- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...

    , JFET
    JFET
    The junction gate field-effect transistor is the simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals...

    , IGFET (MOSFET
    MOSFET
    The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

    ), IGBT, "other types"
  • Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs)
  • Maximum power rating: low, medium, high
  • Maximum operating frequency: low, medium, high, radio frequency
    Radio frequency
    Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

     (RF), microwave
    Microwave
    Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...

     (The maximum effective frequency of a transistor is denoted by the term , an abbreviation for "frequency of transition". The frequency of transition is the frequency at which the transistor yields unity gain).
  • Application: switch, general purpose, audio, high voltage, super-beta, matched pair
  • Physical packaging: through hole
    Through-hole technology
    Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards and soldered to pads on the opposite side either by manual assembly by...

     metal, through hole plastic, surface mount
    Surface-mount technology
    Surface mount technology is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards . An electronic device so made is called a surface mount device...

    , ball grid array
    Ball grid array
    A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...

    , power modules
  • Amplification factor hfe
    Transistor models
    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 models. There exists a variety of different models that...

     (transistor beta)

Thus, a particular transistor may be described as silicon, surface mount, BJT, NPN, low power, high frequency switch.

Bipolar junction transistor



Bipolar transistors are so named because they conduct by using both majority and minority carriers. The bipolar junction transistor (BJT), 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
P-n junction
A p–n junction is formed at the boundary between a P-type and N-type semiconductor created in a single crystal of semiconductor by doping, for example by ion implantation, diffusion of dopants, or by epitaxy .If two separate pieces of material were used, this would...

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).

The BJT has three terminals, corresponding to the three layers of semiconductor – an emitter, a base, and a collector. It is useful in amplifiers because the currents at the emitter and collector are controllable by a relatively small base current." In an NPN transistor operating in the active region, the emitter-base junction is forward biased (electrons and holes recombine at 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 (electrons and holes are formed at, and move away from the junction) 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. 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 FET, 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
Transconductance
Transconductance, also known as mutual conductance, is a property of certain electronic components. Conductance is the reciprocal of resistance; transconductance, meanwhile, is the ratio of the current change at the output port to the voltage change at the input port. It is written as gm...

 than the FET.

Bipolar transistors can be made to conduct by exposure to light, since 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.

Field-effect transistor


The field-effect transistor
Field-effect transistor
The field-effect transistor is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with...

(FET), 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 FETs, 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 () (where VT is the threshold voltage at which drain current begins) in the "space-charge-limited
Space charge
Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space rather than distinct point-like charges...

" region above threshold. A quadratic behavior is not observed in modern devices, for example, at the 65 nm
65 nanometer
The 65 nm process is an advanced lithographic node used in volume CMOS semiconductor fabrication. Printed linewidths can reach as low as 25 nm on a nominally 65 nm process, while the pitch between two lines may be greater than 130 nm.. For comparison, cellular ribosomes are...

 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
JFET
The junction gate field-effect transistor is the simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals...

) and insulated gate FET (IGFET). The IGFET is more commonly known as a metal–oxide–semiconductor FET (MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

), reflecting its original construction from layers of metal (the gate), oxide (the insulation), and semiconductor. Unlike IGFETs, the JFET gate forms a PN diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

 with the channel which lies between the source and drain. Functionally, this makes the N-channel JFET the solid state equivalent of the vacuum tube triode
Triode
A triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electronic amplification device...

 which, similarly, forms a diode between its grid
Control grid
The control grid is an electrode used in thermionic valves used to modulate the flow of electrons in the cathode to anode or plate circuit.- Operation :...

 and cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...

. 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 (MESFET
MESFET
MESFET stands for metal semiconductor field effect transistor. It is quite similar to a JFET in construction and terminology. The difference is that instead of using a p-n junction for a gate, a Schottky junction is used...

s) are JFETs in which the reverse biased PN junction is replaced by a metal–semiconductor Schottky
Walter H. Schottky
Walter Hermann Schottky was a German physicist who played a major early role in developing the theory of electron and ion emission phenomena, invented the screen-grid vacuum tube in 1915 and the pentode in 1919 while working at Siemens, and later made many significant contributions in the areas of...

-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 (microwave frequencies; several GHz).

Unlike bipolar transistors, FETs do not inherently amplify a photocurrent. Nevertheless, there are ways to use them, especially JFETs, as light-sensitive devices, by exploiting the photocurrents in channel–gate or channel–body junctions.

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 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 as the diode junctions would forward bias and conduct if they were enhancement mode devices;
most IGFETs are enhancement-mode types.

Usage of bipolar and field effect transistors


The bipolar junction transistor
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...

 (BJT) was the most commonly used transistor in the 1960s and 70s. Even after MOSFETs became widely available, the BJT remained the transistor of choice for many analog circuits such as amplifiers because of their greater linearity and ease of manufacture. In integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s, the desirable properties of MOSFETs allowed them to capture nearly all market share for digital circuits. Discrete MOSFETs can be applied in transistor applications, including analog circuits, voltage regulators, amplifiers, power transmitters and motor drivers.

Other transistor types



  • Point-contact transistor
    Point-contact transistor
    A point-contact transistor was the first type of solid-state electronic transistor ever constructed. It was made by researchers John Bardeen and Walter Houser Brattain at Bell Laboratories in December 1947. They worked in a group led by physicist William Bradford Shockley...

    , first kind of transistor ever constructed
  • Bipolar junction transistor
    Bipolar junction transistor
    |- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...

     (BJT)
    • Heterojunction bipolar transistor
      Heterojunction bipolar transistor
      The heterojunction bipolar transistor is a type of bipolar junction transistor which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it that can handle signals of very high frequencies, up to several hundred...

      , up to several hundred GHz, common in modern ultrafast and RF circuits
    • Grown-junction transistor
      Grown-junction transistor
      The grown-junction transistor was the first type of bipolar junction transistor made. It was invented by William Shockley at Bell Labs on June 23, 1948. The patent was filed on June 26, 1948. The first germanium prototypes were made in 1949...

      , first kind of BJT
    • Alloy-junction transistor
      Alloy-junction transistor
      The germanium alloy-junction transistor, or alloy transistor, was an early type of bipolar junction transistor, developed at General Electric and RCA in 1951 as an improvement over the earlier grown-junction transistor....

      , improvement of grown-junction transistor
      • Micro-alloy transistor (MAT), speedier than alloy-junction transistor
      • Micro-alloy diffused transistor (MADT), speedier than MAT, a diffused-base transistor
      • Post-alloy diffused transistor (PADT), speedier than MAT, a diffused-base transistor
      • Schottky transistor
      • Surface barrier transistor
    • Drift-field transistor
      Drift-field transistor
      The drift-field transistor, also called the drift transistor or graded base transistor, is a type of high-speed bipolar junction transistor having a doping-engineered electric field in the base to reduce the charge carrier base transit time....

    • Avalanche transistor
      Avalanche transistor
      An avalanche transistor is a bipolar junction transistor designed for operation in the region of its collector-current/collector-to-emitter voltage characteristics beyond the collector to emitter breakdown voltage, called avalanche breakdown region ...

    • Darlington transistor
      Darlington transistor
      In electronics, the Darlington transistor is a compound structure consisting of two bipolar transistors connected in such a way that the current amplified by the first transistor is amplified further by the second one...

      s 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
      Asea Brown Boveri
      ABB is a Swiss-Swedish multinational corporation headquartered in Zürich, Switzerland, and best known for its robotics. ABB operates mainly in the power and automation technology areas. It ranked 143rd in Forbes Ranking ....

       (ABB) 5SNA2400E170100 illustrates just how far power semiconductor technology has advanced. Intended for three-phase power supplies, this device houses three NPN 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.
    • Photo transistor
  • Field-effect transistor
    Field-effect transistor
    The field-effect transistor is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with...

    • Carbon nanotube field-effect transistor
      Carbon nanotube field-effect transistor
      A carbon nanotube field-effect transistor refers to 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...

       (CNFET)
    • JFET
      JFET
      The junction gate field-effect transistor is the simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals...

      , where the gate is insulated by a reverse-biased PN junction
    • MESFET
      MESFET
      MESFET stands for metal semiconductor field effect transistor. It is quite similar to a JFET in construction and terminology. The difference is that instead of using a p-n junction for a gate, a Schottky junction is used...

      , similar to JFET with a Schottky junction instead of PN one
      • High Electron Mobility Transistor (HEMT, HFET, MODFET)
    • MOSFET
      MOSFET
      The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

      , where the gate is insulated by a shallow layer of insulator
    • Inverted-T field effect transistor (ITFET)
    • FinFET, source/drain region shapes fins on the silicon surface.
    • FREDFET
      FREDFET
      A FREDFET is a fast-reverse or fast-recovery epitaxial diode field-effect transistor. This specialised field-effect transistor is designed to provide a very fast recovery of the body diode, making it convenient for driving inductive loads such as electric motors, especially medium-powered...

      , fast-reverse epitaxial diode field-effect transistor
    • Thin film transistor, in LCDs.
    • OFET
      OFET
      An organic field-effect transistor is a field effect transistor using an organic semiconductor in its channel. OFETs can be prepared either by vacuum evaporation of small molecules, by solution-casting of polymers or small molecules, or by mechanical transfer of a peeled single-crystalline organic...

       Organic Field-Effect Transistor, in which the semiconductor is an organic compound
    • Ballistic transistor
      Ballistic transistor
      Ballistic deflection transistors are electronic devices being developed for high-speed integrated circuits. Instead of switching the flow of several electrons using gates, as it is done in field-effect transistors, they try to manipulate the course of single electrons using electromagnetic forces...

    • Floating-gate transistor, for non-volatile storage.
    • FETs used to sense environment
      • Ion-sensitive field effect transistor, to measure ion concentrations in solution.
      • EOSFET
        EOSFET
        An EOSFET or electrolyte-oxide-semiconductor field effect transistor is a FET, like a MOSFET, but with the metal replaced by electrolyte solution for the detection of neuronal activity. Many EOSFETs are integrated in a neurochip....

        , electrolyte-oxide-semiconductor field effect transistor (Neurochip
        Neurochip
        A neurochip is a chip that is designed for the interaction with neuronal cells.- Formation :It is made of silicon that is doped in such a way that it contains EOSFETs that can sense the electrical activity of the neurons in the above-standing physiological electrolyte solution...

        )
      • DNAFET
        DNAFET
        A DNA field-effect transistor is a field-effect transistor which uses the field-effect due to the partial charges of DNA molecules to function as a biosensor. The structure of DNAFETs is similar to that of MOSFETs with the exception of the gate structure which, in DNAFETs, is replaced by a layer...

        , deoxyribonucleic acid field-effect transistor
  • Spacistor
    Spacistor
    The spacistor was a type of transistor developed in the 1950s as an improvement over the point-contact transistor and the later alloy junction transistor. It offered much higher speed than earlier transistors....

  • Diffusion transistor
    Diffusion transistor
    A diffusion transistor is any transistor formed by diffusing dopants into a semiconductor substrate. Diffusion transistors include some types of both bipolar junction transistors and field-effect transistors...

    , formed by diffusing dopants into semiconductor substrate; can be both BJT and FET
  • Unijunction transistor
    Unijunction transistor
    A unijunction transistor is an electronic semiconductor device that has only one junction. The UJT has three terminals: an emitter and two bases . The base is formed by lightly doped n-type bar of silicon. Two ohmic contacts B1 and B2 are attached at its ends. The emitter is of p-type and it is...

    s can be used as simple pulse generators. They comprise a 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 tunnelling junctions. The tunnelling current is controlled by a voltage applied to the gate through a capacitor.
  • Nanofluidic transistor, controls the movement of ions through sub-microscopic, water-filled channels. Nanofluidic transistor, the basis of future chemical processors
  • Multigate devices
    • Tetrode transistor
      Tetrode transistor
      -Early tetrode transistors:There were two types of tetrode transistor developed in the early 1950s as an improvement over the point-contact transistor and the later grown junction transistor and alloy junction transistor. Both offered much higher speed than earlier transistors.*Point-contact...

    • Pentode transistor
      Pentode transistor
      -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 three emitters...

    • Multigate device
      Multigate device
      A multigate device or multiple gate field-effect transistor refers to a MOSFET which incorporates more than one gate into a single device. The multiple gates may be controlled by a single gate electrode, wherein the multiple gate surfaces act electrically as a single gate, or by independent gate...

    • Trigate transistors (Prototype by Intel)
    • Dual gate FETs have a single channel with two gates in cascode
      Cascode
      The cascode is a two-stage amplifier composed of a transconductance amplifier followed by a current buffer. Compared to a single amplifier stage, this combination may have one or more of the following characteristics: higher input-output isolation, higher input impedance, high output impedance,...

      ; a configuration optimized for high frequency amplifiers, mixers, and oscillators.
  • Junctionless Nanowire Transistor (JNT), developed at Tyndall National Institute
    Tyndall National Institute
    Tyndall National Institute in Cork, Ireland named for John Tyndall, scientist, is one of Europe's leading research centres, specialising in ICT hardware research, commercialisation of technology and the education of next generation researchers...

     in Ireland
    Ireland
    Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

    , was the first transistor successfully fabricated without junctions. (Even MOSFET
    MOSFET
    The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

    s have junctions, although its gate is electrically insulated from the region the gate controls.) Junctions are difficult and expensive to fabricate, and, because they are a significant source of current leakage, they waste significant power and generate significant waste heat. Eliminating them held the promise of cheaper and denser microchips. The 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. This method has been described as akin to squeezing a garden hose to gate the flow of water through the hose. The nanowire is heavily n-doped, making it an excellent conductor. Crucially the gate, comprising silicon, is heavily p-doped; and its presence depletes the underlying silicon nanowire thereby preventing carrier flow past the gate.

Part numbers


The types of some transistors can be parsed from the part number. There are three major semiconductor naming standards; in each the alphanumeric prefix provides clues to type of the device:

Japanese Industrial Standard (JIS) has a standard for transistor part numbers. They begin with "2S", e.g. 2SD965, but sometimes the "2S" prefix is not marked on the package – a 2SD965 might only be marked "D965"; 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.
Beginning of Part Number Type of Transistor
2SA high frequency PNP BJTs
2SB audio frequency PNP BJTs
2SC high frequency NPN BJTs
2SD audio frequency NPN BJTs
2SJ P-channel FETs (both JFETs and MOSFETs)
2SK N-channel FETs (both JFETs and MOSFETs)


The Pro Electron
Pro Electron
Pro Electron is the European type designation and registration system for active components .Pro Electron was set up in 1966 in Brussels, Belgium...

 part numbers begin 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 3-digit sequence number (or one letter then 2 digits, for industrial types) follows (and, with early devices, indicated the case type – just as the older system for vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s used the last digit or two to indicate the number of pins, and the first digit or two for the filament voltage). Suffixes may be used, such as a letter (e.g. "C" often means high hFE, 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:
Prefix class Usage Example
AC Germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 small signal transistor
AC126
AF Germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 transistor
AF117
BC Silicon, small signal transistor ("allround") BC548B
BD Silicon, power transistor BD139
BF Silicon, RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 (high frequency) BJT or FET
Fet
Fet is a municipality in Akershus county, Norway. It is part of the Romerike traditional region. The administrative centre of the municipality is the village of Fetsund.Fet was established as a municipality on 1 January 1838...

 
BF245
BS Silicon, switching transistor (BJT
Bipolar
-Medicine:* Bipolar cell* Bipolar cell of the retina* Bipolar disorder** Bipolar I disorder** Bipolar II disorder** Bipolar NOS* Bipolar spectrum-Astronomy:* Bipolar nebula, a two-lobed, axially symmetric nebula...

 or MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

)
BS170
BL Silicon, high frequency, high power (for transmitters) BLW34
BU Silicon, high voltage (for CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

 horizontal deflection circuits)
BU508


The JEDEC
JEDEC
The JEDEC Solid State Technology Association, formerly known as the Joint Electron Devices Engineering Council , is an independent semiconductor engineering trade organization and standardization body...

 transistor device numbers usually start with 2N, indicating a three-terminal device (dual-gate field-effect transistor
Field-effect transistor
The field-effect transistor is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with...

s are four-terminal devices, so begin with 3N), then a 2, 3 or 4-digit sequential number with no significance as to device properties (although low numbers tend to be Germanium devices, because early transistors were mainly Germanium). For example 2N3055
2N3055
The 2N3055 is a silicon NPN power transistor intended for general purpose applications.It was introduced in the early 1960s by RCA using a hometaxial power transistor process, transitioned to an epitaxial base in the mid 1970s. Its numbering follows the JEDEC standard...

 is a silicon NPN power transistor, 2N1301 is a PNP germanium switching transistor. A letter suffix (such as "A") is sometimes used to indicate a newer variant, but rarely gain groupings.

Other schemes


Manufacturers of devices may have their own proprietary numbering system, for example CK722
CK722
The CK722 was the first low cost junction transistor available to the general public. It was a PNP germanium small signal unit. It was introduced by Raytheon in early 1953 for $7.60 each; the price was reduced to $3.50 in late 1954 and to $0.99 in 1956 The CK722s were selected "fall out" from the...

.
Note that a manufacturer's prefix (like "MPF" in MPF102, which originally would denote a Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

 FET
Fet
Fet is a municipality in Akershus county, Norway. It is part of the Romerike traditional region. The administrative centre of the municipality is the village of Fetsund.Fet was established as a municipality on 1 January 1838...

) 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
Fairchild Semiconductor
Fairchild Semiconductor International, Inc. is an American semiconductor company based in San Jose, California. Founded in 1957, it was a pioneer in transistor and integrated circuit manufacturing...

) 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 own 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 Junction FET
Fet
Fet is a municipality in Akershus county, Norway. It is part of the Romerike traditional region. The administrative centre of the municipality is the village of Fetsund.Fet was established as a municipality on 1 January 1838...

, the other the higher-powered MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

 2SJ176).

As older "through-hole" transistors are given Surface-Mount
Surface-mount technology
Surface mount technology is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards . An electronic device so made is called a surface mount device...

 packaged counterparts, they tend to be assigned many different part numbers because manufacturers have their own systems to cope with the variety in pinout
Pinout
In electronics, a pinout is a cross-reference between the contacts, or pins, of an electrical connector or electronic component, and their functions.- Purpose :...

 arrangements and options for dual or matched NPN+PNP 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 standardised in their naming.

Semiconductor material


The first BJTs were made from germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 (Ge). Silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 (Si
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...

) types currently predominate but certain advanced microwave and high performance versions now employ the compound semiconductor material gallium arsenide (GaAs
Gaas
Gaas is a commune in the Landes department in Aquitaine in south-western France....

) and the semiconductor alloy silicon germanium (SiGe
SiGe
SiGe , or silicon-germanium, is a general term for the alloy Si1−xGex which consists of any molar ratio of silicon and germanium. It is commonly used as a semiconductor material in integrated circuits for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors...

). 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 table below; these parameters will vary with increase in temperature, electric field, impurity level, strain, and sundry other factors:
Semiconductor material characteristics
Semiconductor
material
Junction forward
voltage
V @ 25 °C
Electron mobility
m2/(V·s) @ 25 °C
Hole mobility
m2/(V·s) @ 25 °C
Max. junction temp.
°C
Ge 0.27 0.39 0.19 70 to 100
Si 0.71 0.14 0.05 150 to 200
GaAs 1.03 0.85 0.05 150 to 200
Al-Si junction 0.3 150 to 200


The junction forward voltage is the voltage applied to the emitter-base junction of a BJT in order 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 increase in temperature. For a typical silicon junction the change is −2.1 mV/°C. In some circuits special compensating elements (sensistor
Sensistor
Sensistor is a resistor whose resistance changes with temperature.The resistance increases exponentially with temperature, that is the temperature coefficient is positive Sensistor is a resistor whose resistance changes with temperature.The resistance increases exponentially with temperature, that...

s) 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
Electron mobility
In solid-state physics, the electron mobility characterizes how quickly an electron can move through a metal or semiconductor, when pulled by an electric field. In semiconductors, there is an analogous quantity for holes, called hole mobility...

and hole mobility columns show the average speed that electrons and holes diffuse through the semiconductor material with an electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

 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
    Reverse leakage current
    Reverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased.When a semiconductor device is reverse biased it should not conduct any current at all, even though, as a temperature effect, it will form electron-hole pairs at both...

    ;
  • 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 NPN transistor tends to be swifter than an equivalent PNP transistor type. 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
HEMT
High electron mobility transistor , also known as heterostructure FET or modulation-doped FET , is a field effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region, as is generally the case for MOSFET...

), has a heterostructure
Heterojunction
A heterojunction is the interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction...

 (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.

Max. junction temperature values represent a cross section taken from various manufacturers' data sheets. This temperature should not be exceeded or the transistor may be damaged.

Al–Si junction refers to the high-speed (aluminum–silicon) semiconductor–metal barrier diode, commonly known as a Schottky diode
Schottky diode
The Schottky diode is a semiconductor diode with a low forward voltage drop and a very fast switching action...

. This is included in the table because some silicon power IGFETs have a parasitic
Parasitic structure
In a semiconductor device, a parasitic structure is a portion of the device that resembles in structure some other, simpler semiconductor device, and causes the device to enter an unintended mode of operation when subjected to conditions outside of its normal range...

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 are individually packaged. Transistors come in many different semiconductor packages (see images). The two main categories are through-hole
Through-hole technology
Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards and soldered to pads on the opposite side either by manual assembly by...

(or leaded), and surface-mount, also known as surface mount device (SMD
Surface-mount technology
Surface mount technology is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards . An electronic device so made is called a surface mount device...

). The ball grid array (BGA
Ball grid array
A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...

) is the latest surface mount package (currently only for large integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s). 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 rating.

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
Heat sink
A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...

s for enhanced cooling. Additionally, most power transistors have the collector or drain physically connected to the metal enclosoure. 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).

See also



  • 2N3055
    2N3055
    The 2N3055 is a silicon NPN power transistor intended for general purpose applications.It was introduced in the early 1960s by RCA using a hometaxial power transistor process, transitioned to an epitaxial base in the mid 1970s. Its numbering follows the JEDEC standard...

  • Band gap
    Band gap
    In solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the...

  • Chip carrier
    Chip carrier
    A chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...

  • Digital logic
  • Diode
    Diode
    In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

  • Electronic component
    Electronic component
    An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...

  • Integrated circuit
    Integrated circuit
    An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

  • Memristor
    Memristor
    Memristor is a passive two-terminal electrical component envisioned by Leon Chua as a fundamental non-linear circuit element relating charge and magnetic flux linkage...

  • Moore's law
    Moore's Law
    Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....


  • Semiconductor
    Semiconductor
    A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

  • Semiconductor device modeling
    Semiconductor device modeling
    Semiconductor device modeling creates models for the behavior of the electrical devices based on fundamental physics, such as the doping profiles of the devices. It may also include the creation of compact models , which try to capture the electrical behavior of such devices but do not generally...

  • Semiconductor devices
  • Transconductance
    Transconductance
    Transconductance, also known as mutual conductance, is a property of certain electronic components. Conductance is the reciprocal of resistance; transconductance, meanwhile, is the ratio of the current change at the output port to the voltage change at the input port. It is written as gm...

  • Transistor count
    Transistor count
    The transistor count of a device is the number of transistors in the device.Transistor count is the most common measure of integrated circuit complexity. According to Moore's Law, the transistor count of the integrated circuits doubles every two years...

  • Transistor models
    Transistor models
    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 models. There exists a variety of different models that...

  • Transistor–transistor logic
  • Transresistance
  • Very-large-scale integration
    Very-large-scale integration
    Very-large-scale integration is the process of creating integrated circuits by combining thousands of transistors into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device.The first semiconductor...



Directory of external websites with datasheets

  • 2N3904/2N3906, BC182/BC212 and BC546/BC556: Ubiquitous, BJT, general-purpose, low-power, complementary pairs. They have plastic cases and cost roughly ten cents U.S. in small quantities, making them popular with hobbyists.
  • AF107
    AF107
    The AF107 is the European name for an early germanium-based bipolar junction transistor of PNP polarity intended for high frequency use . It shares most of its characteristics with the AF108. Both models use a non-standard round metallic housing of 9 millimetre diameter which is electrically...

    : Germanium, 0.5 watt, 250 MHz PNP BJT.
  • BFP183: Low power, 8 GHz microwave NPN BJT.
  • LM394: "supermatch pair", with two NPN BJTs on a single substrate.
  • 2N2219A/2N2905A: BJT, general purpose, medium power, complementary pair. With metal cases they are rated at about one watt.
  • 2N3055/MJ2955: For years, the venerable NPN 2N3055 has been the "standard" power transistor. Its complement, the PNP MJ2955 arrived later. These 1 MHz, 15 A, 60 V, 115 W BJTs are used in audio power amplifiers, power supplies, and control.
  • 2SC3281/2SA1302: Made by Toshiba
    Toshiba
    is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...

    , these BJTs have low-distortion characteristics and are used in high-power audio amplifiers. They have been widely counterfeitedhttp://sound.westhost.com/counterfeit.htm.
  • BU508: NPN, 1500 V power BJT. Designed for television
    Television
    Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

     horizontal deflection, its high voltage capability also makes it suitable for use in ignition systems.
  • MJ11012/MJ11015: 30 A, 120 V, 200 W, high power Darlington complementary pair BJTs. Used in audio amplifiers, control, and power switching.
  • 2N5457/2N5460: JFET
    JFET
    The junction gate field-effect transistor is the simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals...

     (depletion mode), general purpose, low power, complementary pair.
  • BSP296/BSP171: IGFET (enhancement mode), medium power, near complementary pair. Used for logic level conversion and driving power transistors in amplifiers.
  • IRF3710/IRF5210: IGFET (enhancement mode), 40 A, 100 V, 200 W, near complementary pair. For high-power amplifiers and power switches, especially in automobiles.

External links