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[[Image:Transistorer (croped).jpg|thumb|upright|Assorted discrete transistors. Packages in order from top to bottom: [[TO-3]], [[TO-126]], [[TO-92]], [[Small-outline transistor|SOT-23]]]]
 
A '''transistor''' is a [[semiconductor device]] used to [[Electronic amplifier|amplify]] and [[switch]] [[Electronics|electronic]] signals and [[electrical power]]. It is composed of [[semiconductor]] material with at least three terminals for connection to an external circuit. A voltage or [[Electric current|current]] applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) [[electric power|power]] can be higher than the controlling (input) power, a transistor can [[gain|amplify]] a signal. Today, some transistors are packaged individually, but many more are found embedded in [[integrated circuit]]s.
 
The transistor is the fundamental building block of modern [[electronic device]]s, and is ubiquitous in modern electronic systems. Following its development in 1947 by [[John Bardeen]], [[Walter Brattain]], and [[William Shockley]], the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper [[radio]]s, [[calculator]]s, and [[computer]]s, among other things.  The transistor is on the list of [[list of IEEE milestones|IEEE milestones]] in electronics, and the inventors were jointly awarded the 1956 [[Nobel Prize in Physics]] for their achievement.
 
==History==
{{Main|History of the transistor}}
[[Image:Replica-of-first-transistor.jpg|thumb|A replica of the first working transistor.]]
 
The [[thermionic]] [[triode]], a [[vacuum tube]] invented in 1907, propelled the [[electronics]] age forward, enabling amplified [[radio]] technology and long-distance [[telephony]].  The triode, however, was a fragile device that consumed a lot of power.  Physicist [[Julius Edgar Lilienfeld]] filed a patent for a [[field-effect transistor]] (FET) in Canada in 1925, which was intended to be a [[Solid-state (electronics)|solid-state]] replacement for the triode.<ref>Vardalas, John, [http://www.todaysengineer.org/2003/May/history.asp Twists and Turns in the Development of the Transistor] ''IEEE-USA Today's Engineer'', May 2003.</ref><ref>Lilienfeld, Julius Edgar, "Method and apparatus for controlling electric current" {{US patent|1745175}} 1930-01-28 (filed in Canada 1925-10-22, in US 1926-10-08).</ref> Lilienfeld also filed identical patents in the United States in 1926<ref>{{cite web|title=Method And Apparatus For Controlling Electric Currents|publisher=United States Patent and Trademark Office|url=http://www.google.com/patents?id=uBFMAAAAEBAJ&printsec=abstract#v=onepage&q&f=false}}</ref> and 1928.<ref>{{cite web|title=Amplifier For Electric Currents|publisher=United States Patent and Trademark Office|url=http://www.google.com/patents?id=jvhAAAAAEBAJ&printsec=abstract#v=onepage&q&f=false}}</ref><ref>{{cite web|title=Device For Controlling Electric Current|publisher=United States Patent and Trademark Office|url=http://www.google.com/patents?id=52BQAAAAEBAJ&printsec=abstract#v=onepage&q&f=false}}</ref> 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 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.<ref name="todaysengineer.org">{{cite web|title=Twists and Turns in the Development of the Transistor|publisher=Institute of Electrical and Electronics Engineers, Inc.|url=http://www.todaysengineer.org/2003/May/history.asp}}</ref> In 1934, German inventor [[Oskar Heil]] patented a similar device.<ref>[http://v3.espacenet.com/publicationDetails/biblio?CC=GB&NR=439457&KC=&FT=E Heil, Oskar, "Improvements in or relating to electrical amplifiers and other control arrangements and devices"], Patent No. GB439457, European Patent Office, filed in Great Britain 1934-03-02, published 1935-12-06 (originally filed in Germany 1934-03-02).</ref>
[[File:Bardeen Shockley Brattain 1948.JPG|thumb|left|John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948.]]
From November 17, 1947 to December 23, 1947, [[John Bardeen]] and [[Walter Brattain]] at [[AT&T Corporation|AT&T]]'s [[Bell Labs]] in the United States, performed experiments and observed that when two gold point contacts were applied to a crystal of [[germanium]], a signal was produced with the output power greater than the input.<ref>{{cite web|title=November 17 – December 23, 1947: Invention of the First Transistor|publisher=American Physical Society|url=http://www.aps.org/publications/apsnews/200011/history.cfm}}</ref> Solid State Physics Group leader [[William Shockley]] saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term ''transistor'' was coined by [[John R. Pierce]] as a [[portmanteau]] of the term "transfer resistor".<ref>{{cite book|author=David Bodanis|title=Electric Universe|publisher=Crown Publishers, New York|year=2005|isbn=0-7394-5670-9}}</ref><ref>{{cite encyclopedia|encyclopedia=American Heritage Dictionary|edition=3rd|year=1992|publisher=Houghton Mifflin|location=Boston|title=transistor}}</ref> According to Lillian Hoddeson and Vicki Daitch, authors of a biography of John Bardeen, 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]].<ref name="todaysengineer.org"/> In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956 [[Nobel Prize in Physics]] "for their researches on semiconductors and their discovery of the transistor effect."<ref>{{cite web|title=The Nobel Prize in Physics 1956|url=http://nobelprize.org/nobel_prizes/physics/laureates/1956/}}</ref>
 
In 1948, the point-contact transistor was independently invented by German physicists [[Herbert Mataré]] and [[Heinrich Welker]] while working at the Compagnie des Freins et Signaux, a [[Westinghouse Electric (1886)|Westinghouse]] subsidiary located in [[Paris]]. Mataré had previous experience in developing [[Cat's-whisker detector|crystal rectifiers]] from [[silicon]] and germanium in the German [[radar]] effort during [[World War II]]. Using this knowledge, he began researching the phenomenon of "[[Interference (wave propagation)|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 Labs' 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.<ref>{{cite web|title=1948 - The European Transistor Invention|publisher=Computer History Museum|url=http://www.computerhistory.org/semiconductor/timeline/1948-European.html}}</ref>
 
[[File:Philco Surface Barrier transistor=1953.jpg|thumb|Philco surface-barrier transistor developed and produced in 1953]]
The first high-frequency transistor was the [[surface-barrier transistor|surface-barrier germanium transistor]] developed by [[Philco]] in 1953, capable of operating up to {{nowrap|60 MHz}}.<ref>Proceeding of the IRE, Dec 1953, Author: W.E. Bradley - Philco Corp.,Research Division, Volume 41 issue 12, pages 1702-1706</ref> 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.<ref>Wall Street Journal, Dec 04 1953, page 4, Article "Philco Claims Its Transistor Outperforms Others Now In Use"</ref><ref>Electronics magazine, January 1954, Article "Electroplated Transistors Announced"</ref>  The first [[Transistor radio|all-transistor car radio]], which was produced in 1955 by [[Chrysler]] and Philco, used these transistors in its circuitry and also they were the first suitable for high-speed computers.<ref>Wall Street Journal, "Chrysler Promises Car Radio With Transistors Instead of Tubes in '56", April 28th 1955, page 1</ref><ref>Los Angeles Times, May 08, 1955, page A20, Article: "Chrysler Announces New Transistor Radio"</ref><ref>Philco TechRep Division Bulletin, May–June 1955, Volume 5 Number 3, page 28</ref><ref>Article" Some Recollections of the Philco Transac S-2000", Author: Saul Rosen - Purdue University Computer Science Dept., June 1991, page 2</ref>
 
The first working silicon transistor was developed at Bell Labs on January 26, 1954 by Morris Tanenbaum.<ref>IEEE Spectrum, The Lost History of the Transistor, Author: Michael Riordan, May 2004, pp 48-49</ref> The first commercial silicon transistor was produced by [[Texas Instruments]] in 1954.<ref>J. Chelikowski, "Introduction: Silicon in all its Forms", ''Silicon: evolution and future of a technology'' (Editors: P. Siffert, E. F. Krimmel), p.1, Springer, 2004 ISBN 3-540-40546-1.</ref> This was the work of [[Gordon Teal]], an expert in growing crystals of high purity, who had previously worked at Bell Labs.<ref>Grant McFarland, ''Microprocessor design: a practical guide from design planning to manufacturing'', p.10, McGraw-Hill Professional, 2006 ISBN 0-07-145951-0.</ref> The first [[MOSFET|MOS]] transistor actually built was by Kahng and Atalla at Bell Labs in 1960.<ref>W. Heywang, K. H. Zaininger, "Silicon: The Semiconductor Material", ''Silicon: evolution and future of a technology'' (Editors: P. Siffert, E. F. Krimmel), p.36, Springer, 2004 ISBN 3-540-40546-1.</ref>
 
==Importance==
[[File:Darlington transistor MJ1000.jpg|thumb|A [[Darlington transistor]] opened up so the actual transistor chip (the small square) can be seen inside.  A Darlington transistor is effectively two transistors on the same chip.  One transistor is much larger than the other, but both are large in comparison to transistors in [[large-scale integration]] because this particular example is intended for power applications.]]
The transistor is the key active component in practically all modern [[electronics]]. Many consider it to be one of the greatest inventions of the 20th century.<ref>{{cite book|title=Roadmap to Entrepreneurial Success|author=Robert W. Price|publisher=AMACOM Div American Mgmt Assn|year=2004|isbn=978-0-8144-7190-6|page=42|url=http://books.google.com/?id=q7UzNoWdGAkC&pg=PA42&dq=transistor+inventions-of-the-twentieth-century}}</ref> Its importance in today's society rests on its ability to be [[mass production|mass-produced]] using a highly automated process ([[semiconductor device fabrication]]) that achieves astonishingly low per-transistor costs. The invention of the first transistor at [[Bell Labs]] was named an [[List of IEEE milestones|IEEE Milestone]] in 2009.<ref>{{cite web |url=http://www.ieeeghn.org/wiki/index.php/Milestones:Invention_of_the_First_Transistor_at_Bell_Telephone_Laboratories,_Inc.,_1947 |title=Milestones:Invention of the First Transistor at Bell Telephone Laboratories, Inc., 1947 |author= |date= |work=IEEE Global History Network |publisher=IEEE |accessdate=3 August 2011}}</ref>
 
Although several companies each produce over a billion individually packaged (known as ''[[Discrete transistor|discrete]]'') transistors every year,<ref>[http://www.globalsources.com/gsol/I/FET-MOSFET/a/9000000085806.htm FETs/MOSFETs: Smaller apps push up surface-mount supply]</ref>
the vast majority of transistors are now produced in [[integrated circuits]] (often shortened to ''IC'', ''microchips'' or simply ''chips''), along with [[diode]]s, [[resistor]]s, [[capacitor]]s and other [[electronic component]]s, to produce complete electronic circuits. A [[logic gate]] consists of up to about twenty transistors whereas an advanced microprocessor, as of 2009, can use as many as 3 billion transistors ([[MOSFET]]s).<ref>"[http://news.cnet.com/8301-13512_3-10369441-23.html ATI and Nvidia face off]." Oct 7, 2009.  Retrieved on Feb 2, 2011.</ref>
"About 60 million transistors were built in 2002 ... for [each] man, woman, and child on Earth."<ref>Turley, J. (December 18, 2002).[http://www.eetimes.com/discussion/other/4024488/The-Two-Percent-Solution The Two Percent Solution]. Embedded.com.</ref>
 
The transistor's low cost, flexibility, and reliability have made it a ubiquitous device. Transistorized [[mechatronics|mechatronic]] circuits have replaced [[cam timer|electromechanical devices]] in controlling appliances and machinery. It is often easier and cheaper to use a standard [[microcontroller]] and write a [[computer program]] to carry out a control function than to design an equivalent mechanical control function.
 
==Simplified operation==
{{unreferenced section|date=November 2010}}
[[Image:Transistor Simple Circuit Diagram with NPN Labels.svg|thumb|A simple circuit diagram to show the labels of a n–p–n bipolar transistor.]]
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]]. A transistor can control its output in proportion to the input signal; that is, it can act as an [[amplifier]]. 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 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. 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''<sub>BE</sub>.
 
===Transistor as a switch===
 
[[Image:Transistor as switch.svg|thumb|150px|BJT used as an electronic switch, in grounded-emitter configuration.]]
 
Transistors are commonly used as electronic switches, both for high-power applications such as [[switched-mode power supply|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 emitter and collector currents rise exponentially. The collector voltage drops because of reduced resistance from collector to 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 current is flowing from collector to emitter freely. When saturated, the switch is said to be ''on''.<ref>{{cite book|last=Kaplan|first=Daniel|title=Hands-On Electronics|year=2003|publisher=Cambridge University Press|location=New York|isbn=978-0-511-07668-8|pages=47–54, 60–61}}</ref>
 
Providing sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a relatively large current in the collector to be switched 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 light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated.
 
In any switching circuit, values of input voltage would be chosen such that the output is either completely off,<ref>apart from a small value due to leakage currents</ref> 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===
 
[[File:NPN common emitter AC.svg|thumb|200px|Amplifier circuit, common-emitter configuration with a voltage-divider bias circuit.]]
 
The [[common-emitter amplifier]] is designed so that a small change in voltage (''V''<sub>in</sub>) 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 ''V''<sub>in</sub> produce large changes in ''V''<sub>out</sub>.
 
Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.
 
From [[mobile phone]]s to [[television]]s, vast numbers of products include amplifiers for [[sound reproduction]], [[Transmitter|radio transmission]], and [[signal processing]]. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.
 
Modern transistor audio amplifiers of up to a few hundred [[watt]]s are common and relatively inexpensive.
 
==Comparison with vacuum tubes==
Prior to the development of transistors, [[vacuum tube|vacuum (electron) tube]]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
*No power consumption by a cathode heater.
*Small size and minimal weight, allowing the development of miniaturized electronic devices.
*Low operating voltages compatible with batteries of only a few cells.
*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]] in audio applications.
 
===Limitations===
*Silicon transistors can age and fail.<ref>John Keane and Chris H. Kim, [http://spectrum.ieee.org/semiconductors/processors/transistor-aging "Transistor Aging,"] ''IEEE Spectrum'' (web feature), April 25, 2011.</ref>
*High-power, high-frequency operation, such as that used in over-the-air [[television|television broadcasting]], is better achieved in vacuum tubes due to improved [[electron mobility]] in a vacuum.
*Solid-state devices are more vulnerable to [[electrostatic discharge]] in handling and operation
*A vacuum tube momentarily overloaded will just get a little hotter; solid-state devices have less mass to absorb the heat due to overloads, in proportion to their rating
*Sensitivity to radiation and cosmic rays (special radiation-hardened chips are used for spacecraft devices).
*Vacuum tubes create a distortion, the so-called [[tube sound]], that some people find to be more tolerable to the ear.<ref name=Veen1>{{Cite conference
| last = van der Veen
| first = M.
| title = Universal system and output transformer for valve amplifiers
| booktitle = 118th AES Convention, Barcelona, Spain
| year = 2005
| url = http://www.mennovanderveen.nl/nl/download/download_3.pdf
}}</ref>
 
==Types==
{{float_begin|side=right}}
|- style="text-align:center;"
|[[Image:BJT PNP symbol.svg|80px]]||PNP||[[Image:JFET P-Channel Labelled.svg|80px]]||P-channel
|- style="text-align:center;"
|[[Image:BJT NPN symbol.svg|80px]]||NPN||[[Image:JFET N-Channel Labelled.svg|80px]]||N-channel
|- style="text-align:center;"
|BJT||||JFET||
{{float_end|caption=BJT and JFET symbols}}
 
{{float_begin|side=right}}
|- style="text-align:center;"
|[[Image:JFET P-Channel Labelled.svg|80px]]||[[Image:IGFET P-Ch Enh Labelled.svg|80px]]||[[Image:IGFET P-Ch Enh Labelled simplified.svg|80px]]||[[Image:IGFET P-Ch Dep Labelled.svg|80px]]||P-channel
|- style="text-align:center;"
|[[Image:JFET N-Channel Labelled.svg|80px]]||[[Image:IGFET N-Ch Enh Labelled.svg|80px]]||[[Image:IGFET N-Ch Enh Labelled simplified.svg|80px]]||[[Image:IGFET N-Ch Dep Labelled.svg|80px]]||N-channel
|- style="text-align:center;"
|JFET||colspan="2"|MOSFET enh||MOSFET dep
{{float_end|caption=JFET and IGFET symbols}}
 
Transistors are categorized by
*[[List of semiconductor materials|Semiconductor material]] (date first used): the [[metalloid]]s [[germanium]] (1947) and [[silicon]] (1954)— in [[amorphous silicon|amorphous]], [[polycrystalline silicon|polycrystalline]] and [[monocrystalline silicon|monocrystalline]] form; the [[chemical compound|compound]]s [[gallium arsenide]] (1966) and [[silicon carbide]] (1997), the [[alloy]] [[silicon-germanium]] (1989), the [[allotrope of carbon]] [[graphene#Electronics|graphene]] (research ongoing since 2004), etc.—see [[#Semiconductor material|Semiconductor material]]
*Structure: [[Bipolar junction transistor|BJT]], [[JFET]], IGFET ([[MOSFET]]), [[insulated-gate bipolar transistor]], "other types"
*[[Electrical polarity]] (positive and negative): [[NPN transistor|n–p–n]], [[PNP transistor|p–n–p]] (BJTs); n-channel, p-channel (FETs)
*Maximum [[power rating]]: low, medium, high
*Maximum operating frequency: low, medium, high, [[radio frequency|radio]] (RF), [[microwave]] frequency (the maximum effective frequency of a transistor is denoted by the term <math>f_\mathrm{T}</math>, an abbreviation for [[gain–bandwidth product#Transistors|transition frequency]]—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 technology|through-hole]] metal, through-hole plastic, [[Surface-mount technology|surface mount]], [[ball grid array]], power modules—see [[#Packaging|Packaging]]
*Amplification factor [[transistor models|h<sub>fe</sub>]], β<sub>F</sub> ([[transistor beta]])<ref>{{cite web|title=Transistor Example|url=http://www.bcae1.com/transres.htm}} 071003 bcae1.com</ref> or g<sub>m</sub> ([[transconductance]]).
Thus, a particular transistor may be described as ''silicon, surface-mount, BJT, n–p–n, low-power, high-frequency switch''.
 
===Bipolar junction transistor (BJT)===
{{Main|Bipolar junction transistor}}
Bipolar transistors are so named because they conduct by using both majority and minority [[charge carriers in semiconductors|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]]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 amplifiers because the currents at the emitter and collector are controllable by a relatively small base current."<ref name=Streetman>{{cite book|last=Streetman|first=Ben|authorlink=Ben G. Streetman|title=Solid State Electronic Devices|year=1992|publisher=Prentice-Hall|location=Englewood Cliffs, NJ|isbn=0-13-822023-9|pages=301–305}}</ref> In an n–p–n transistor operating in the active region, the emitter–base junction is forward biased ([[electron]]s and [[electron hole|hole]]s 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.<ref name=Streetman/> Collector current is approximately β (common-emitter current gain) times the base current. It is typically greater than 100 for small-signal transistors but can be smaller in transistors designed for high-power applications.
 
Unlike the field-effect transistor (see below), the BJT is a low–input-impedance device. Also, as the base–emitter voltage (''V<sub>be</sub>'') is increased the base–emitter current and hence the collector–emitter current (''I<sub>ce</sub>'') increase exponentially according to the [[diode modelling#Shockley diode model|Shockley diode model]] and the [[Ebers-Moll model]]. Because of this exponential relationship, the BJT has a higher [[transconductance]] than the FET.
 
Bipolar transistors can be made to conduct by exposure to light, because 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 [[phototransistor]]s.
 
===Field-effect transistor (FET)===
{{Main|Field-effect transistor|MOSFET|JFET}}
 
The ''[[field-effect transistor]]'', sometimes called a ''unipolar transistor'', uses either electrons (in ''n-channel FET'') or holes (in ''p-channel FET'') for conduction. The four terminals of the FET are named ''source'', ''gate'', ''drain'', and ''body'' (''substrate''). On most FETs, the body is connected to the source inside the package, and this will be assumed for the following description.
 
In a FET, the drain-to-source current flows via a conducting channel that connects the ''source'' region to the ''drain'' region. The conductivity is varied by the electric field that is produced when a voltage is applied between the gate and source terminals; hence the current flowing between the drain and source is controlled by the voltage applied between the gate and source. As the gate–source voltage (''V<sub>gs</sub>'') is increased, the drain–source current (''I<sub>ds</sub>'') increases exponentially for ''V<sub>gs</sub>'' below threshold, and then at a roughly quadratic rate (<math>I_{ds} \propto (V_{gs}-V_T)^2</math>) (where ''V<sub>T</sub>'' is the threshold voltage at which drain current begins)<ref name=horowitz-hill>{{cite book|last=Horowitz|first=Paul|authorlink=Paul Horowitz|coauthors=[[Winfield Hill]]|title=[[The Art of Electronics]]|edition=2nd|year=1989|publisher=Cambridge University Press|isbn=0-521-37095-7|page=115}}</ref> in the "[[space charge|space-charge-limited]]" region above threshold. A quadratic behavior is not observed in modern devices, for example, at the [[65 nanometer|65 nm]] technology node.<ref name=Sansen>
{{cite book|author=W. M. C. Sansen|title=Analog design essentials|year= 2006|page=§0152, p. 28|publisher=Springer|location=New York ; Berlin|isbn=0-387-25746-2|url=http://worldcat.org/isbn/0387257462}}</ref>
 
For low noise at narrow [[bandwidth (signal processing)|bandwidth]] the higher input resistance of the FET is advantageous.
 
FETs are divided into two families: ''junction FET'' ([[JFET]]) and ''insulated gate FET'' (IGFET). The IGFET is more commonly known as a ''metal–oxide–semiconductor FET'' ([[MOSFET]]), reflecting its original construction from layers of metal (the gate), oxide (the insulation), and semiconductor. Unlike IGFETs, the JFET gate forms a [[p–n diode]] with the channel which lies between the source and drain. Functionally, this makes the n-channel JFET the solid-state equivalent of the vacuum tube [[triode]] which, similarly, forms a diode between its [[Control grid|grid]] and [[cathode]]. Also, both devices operate in the ''depletion mode'', they both have a high input impedance, and they both conduct current under the control of an input voltage.
 
Metal–semiconductor FETs ([[MESFET]]s) are JFETs in which the [[Reverse-biased|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 (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 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;
most IGFETs are enhancement-mode types.
 
===Usage of bipolar and field-effect transistors===
The [[bipolar junction transistor]] (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 circuits, 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===
[[File:Transistor on portuguese pavement.jpg|thumb|right|270px|Transistor symbol drawn on [[Portuguese pavement]] in the [[University of Aveiro]].]]
{{Cleanup-list|date=September 2009}}
{{for|early bipolar transistors|Bipolar junction transistor#Bipolar transistors}}
*[[Bipolar junction transistor]]
**[[Heterojunction bipolar transistor]], up to several hundred GHz, common in modern ultrafast and RF circuits
**[[Schottky transistor]]
**[[Avalanche transistor]]
**[[Darlington transistor]]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 transistor]]s (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'' illustrates just how far power semiconductor technology has advanced.<ref>{{cite web|url=http://library.abb.com/GLOBAL/SCOT/scot256.nsf/VerityDisplay/E700072B04381DD9C12571FF002D2CFE/$File/5SNA%202400E170100_5SYA1555-03Oct%2006.pdf |title=IGBT Module 5SNA 2400E170100 |format=PDF |date= |accessdate=2012-06-30}}</ref> Intended for three-phase power supplies, this device houses three n–p–n IGBTs in a case measuring 38 by 140 by 190&nbsp;mm and weighing 1.5&nbsp;kg. Each IGBT is rated at 1,700 volts and can handle 2,400 amperes.
**[[Photo transistor]]
**[[Multiple-emitter transistor]], used in [[transistor–transistor logic]]
**[[Multiple-base transistor]], used to amplify very-low-level signals in noisy environments such as the pickup of a [[record player]] or [[RF front end|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]]ally.<ref>Zhong Yuan Chang, Willy M. C. Sansen, ''Low-Noise Wide-Band Amplifiers in Bipolar and CMOS Technologies'', page 31, Springer, 1991 ISBN 0792390962.</ref>
*[[Field-effect transistor]]
**[[Carbon nanotube field-effect transistor]] (CNFET)
**[[JFET]], where the gate is insulated by a reverse-biased p–n junction
**[[MESFET]], similar to JFET with a Schottky junction instead of a p–n junction
***[[High-electron-mobility transistor]] (HEMT, HFET, MODFET)
**[[MOSFET]], where the gate is insulated by a shallow layer of insulator
**[[ITFET|Inverted-T field-effect transistor]] (ITFET)
**[[FinFET]], source/drain region shapes fins on the silicon surface.
**[[FREDFET]], fast-reverse epitaxial diode field-effect transistor
**[[Thin-film transistor]], in LCDs.
**[[Organic field-effect transistor]] (OFET), in which the semiconductor is an organic compound
**[[Ballistic transistor]]
**[[Floating-gate transistor]], for non-volatile storage.
**FETs used to sense environment
***[[ISFET|Ion-sensitive field effect transistor]] (IFSET), to measure ion concentrations in solution.
***[[EOSFET]], electrolyte-oxide-semiconductor field-effect transistor ([[Neurochip]])
***[[DNAFET]], deoxyribonucleic acid field-effect transistor
*[[Diffusion transistor]], formed by diffusing dopants into semiconductor substrate; can be both BJT and FET
*[[Unijunction transistor]]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 transistor]]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.<ref>{{cite web|url=http://snow.stanford.edu/~shimbo/set.html |title=Single Electron Transistors |publisher=Snow.stanford.edu |date= |accessdate=2012-06-30}}</ref>
*[[Nanofluidic transistor]], controls the movement of ions through sub-microscopic, water-filled channels.<ref>{{cite web|last=Sanders |first=Robert |url=http://www.berkeley.edu/news/media/releases/2005/06/28_transistor.shtml |title=Nanofluidic transistor, the basis of future chemical processors |publisher=Berkeley.edu |date=2005-06-28 |accessdate=2012-06-30}}</ref>
*[[Multigate device]]s
**[[Tetrode transistor]]
**[[Pentode transistor]]
**[[Trigate transistors]] (Prototype by Intel)
**'''Dual-gate FETs''' have a single channel with two gates in [[cascode]]; a configuration optimized for ''high-frequency amplifiers'', ''mixers'', and [[oscillators]].
*Junctionless nanowire transistor (JNT), developed at [[Tyndall National Institute]] in [[Ireland]], was the first transistor successfully fabricated without junctions. (Even [[MOSFET]]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.
*Vacuum-channel transistor: In 2012, NASA and the National Nanofab Center in South Korea were reported to have built a prototype vacuum-channel transistor in only 150 nanometers in size, can be manufactured cheaply using standard silicon semiconductor processing, can operate at high speeds even in hostile environments, and could consume just as much power as a standard transistor.<ref>[http://www.gizmag.com/nasa-vacuum-channel-transistor/22626/ The return of the vacuum tube?]</ref>
 
==Part numbering standards / specifications==
 
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)===
{|class="wikitable" style="float:right; margin:10px;"
|+ JIS Transistor Prefix Table
|-
! Prefix !! Type of transistor
|-
|2SA||high-frequency p–n–p BJTs
|-
|2SB||audio-frequency p–n–p BJTs
|-
|2SC||high-frequency n–p–n BJTs
|-
|2SD||audio-frequency n–p–n BJTs
|-
|2SJ||P-channel FETs (both JFETs and MOSFETs)
|-
|2SK||N-channel FETs (both JFETs and MOSFETs)
|}
The ''[[JIS semiconductor designation|JIS-C-7012]]'' specification for transistor part numbers starts with "2S",<ref>{{cite web|url=http://www.clivetec.0catch.com/Transistors.htm#JIS |title=Clive TEC Transistors Japanese Industrial Standards |publisher=Clivetec.0catch.com |date= |accessdate=2012-06-30}}</ref> 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 h<sub>FE</sub> (gain) groupings.
 
===European Electronic Component Manufacturers Association (EECA)===
 
The [[Pro Electron]] standard, the European Electronic Component Manufacturers Association part numbering 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 3-digit sequence number (or one letter then 2 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<sub>FE</sub>, such as in: BC549C<ref>{{cite web|url=http://www.fairchildsemi.com/ds/BC/BC549.pdf |title=Datasheet for BC549, with A,B and C gain groupings |format=PDF |date= |accessdate=2012-06-30}}</ref>) or other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A<ref>{{cite web|url=http://www.datasheetcatalog.org/datasheet/philips/BUK854-800A.pdf |title=Datasheet for BUK854-800A (800volt IGBT) |format=PDF |date= |accessdate=2012-06-30}}</ref>). The more common prefixes are:
 
{|class="wikitable"
|+ Pro Electron / EECA Transistor Prefix Table
|-
! Prefix class !! Type and usage  !! Example !! Equivalent !! Reference
|-
|AC||[[Germanium]] small-signal [[Audio Frequency|AF]] transistor || AC126 || NTE102A || [http://www.weisd.com/store2/NTE102A.pdf Datasheet]
|-
|AD||[[Germanium]] [[Audio Frequency|AF]] power transistor || AD133 || NTE179 || [http://www.weisd.com/store2/nte179.pdf Datasheet]
|-
|AF||[[Germanium]] small-signal [[Radio Frequency|RF]] transistor || AF117 || NTE160 || [http://www.weisd.com/store2/nte160.pdf Datasheet]
|-
|AL||[[Germanium]] [[Radio Frequency|RF]] power transistor || ALZ10 || NTE100 || [http://www.weisd.com/store2/nte100.pdf Datasheet]
|-
|AS||[[Germanium]] switching transistor || ASY28 || NTE101 || [http://www.weisd.com/store2/NTE101.pdf Datasheet]
|-
|AU||[[Germanium]] power switching transistor || AU103 || NTE127 || [http://www.weisd.com/store2/nte127.pdf Datasheet]
|-
|BC||Silicon, small-signal transistor ("general purpose") || [[BC548]] || [[2N3904]] || [http://www.fairchildsemi.com/ds/BC/BC547.pdf Datasheet]
|-
|BD||Silicon, power transistor || BD139 || NTE375 || [http://www.fairchildsemi.com/ds/BD/BD135.pdf Datasheet]
|-
|BF||Silicon, [[Radio Frequency|RF]] (high frequency) [[BJT]] or [[FET]] || BF245 || NTE133 || [http://www.onsemi.com/pub_link/Collateral/BF245A-D.PDF Datasheet]
|-
|BS||Silicon, switching transistor (BJT or [[MOSFET]]) || [[BS170]] || [[2N7000]] || [http://www.fairchildsemi.com/ds/BS/BS170.pdf Datasheet]
|-
|BL||Silicon, high frequency, high power (for transmitters) || BLW60 || NTE325 || [http://www.datasheetcatalog.org/datasheet/philips/BLW60.pdf Datasheet]
|-
|BU||Silicon, high voltage (for [[Cathode ray tube|CRT]] horizontal deflection circuits) || BU2520A || NTE2354 || [http://www.datasheetcatalog.org/datasheet/philips/BU2520A.pdf Datasheet]
|-
|CF||[[Gallium Arsenide]] small-signal [[Microwave]] transistor ([[MESFET]])&nbsp;|| CF739 || — || [http://www.kesun.com/pdf/rf%20transistor/CF739.pdf Datasheet]
|-
|CL||[[Gallium Arsenide]] [[Microwave]] power transistor ([[Field-effect transistor|FET]]) || CLY10 || — || [http://www.datasheetcatalog.org/datasheet/siemens/CLY10.pdf Datasheet]
|}
 
===Joint Electron Devices Engineering Council (JEDEC)===
 
The [[JEDEC|JEDEC ''EIA370'']] transistor device numbers usually start with "2N", indicating a three-terminal device (dual-gate [[field-effect transistor]]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 early devices with low numbers tend to be germanium). 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.
 
===Proprietary===
 
Manufacturers of devices may have their own proprietary numbering system, for example [[CK722]].
Note that a manufacturer's prefix (like "MPF" in MPF102, which originally would denote a [[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 own codes, such as the [[UK CV series|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<ref>{{cite web|url=http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv010.cgi?read=27258 |title=Richard Freeman's HP Part numbers Crossreference |publisher=Hpmuseum.org |date= |accessdate=2012-06-30}}</ref><ref>[http://www.sphere.bc.ca/test/hp-parts/300-hpxref.pdf Transistor–Diode Cross Reference – H.P. Part Numbers to JEDEC (pdf)]</ref> which is also assigned the CV number: CV7763<ref>{{cite web|url=http://www.qsl.net/g8yoa/cv_table.html |title=CV Device Cross-reference by Andy Lake |publisher=Qsl.net |date= |accessdate=2012-06-30}}</ref>
 
===Naming problems===
With so many independent naming schemes, and the abbreviation of part numbers when printed on the devices, ambiguity sometimes occurs. For example two different devices may be marked "J176" (one the J176 low-power Junction [[FET]], the other the higher-powered [[MOSFET]] 2SJ176).
 
As older "through-hole" transistors are given [[Surface-mount technology|surface-mount]] packaged counterparts, they tend to be assigned many different part numbers because manufacturers have their own 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===
{|class="wikitable" style="float:right; margin:10px;"
|+Semiconductor material characteristics
!Semiconductor <br> material
!Junction forward <br> voltage <br> V @ 25 °C
!Electron mobility <br> m<sup>2</sup>/(V·s) @ 25 °C
!Hole mobility <br> m<sup>2</sup>/(V·s) @ 25 °C
!Max.<br>junction temp.<br>°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 first BJTs were made from [[germanium]] (Ge). [[Silicon]] (Si) types currently predominate but certain advanced microwave and high-performance versions now employ the ''compound semiconductor'' material [[gallium arsenide]] (GaAs) and the ''semiconductor 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 table to the right; these parameters will vary with 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 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.<ref name=Sedra>
{{cite book|author=A.S. Sedra and K.C. Smith|title=Microelectronic circuits|year=2004|pages=397 and Figure 5.17|publisher=Oxford University Press|edition=Fifth|location=New York|isbn=0-19-514251-9}}</ref> In some circuits special compensating elements ([[sensistor]]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]]'' 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 [[Reverse leakage current|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 [[heterojunction|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&nbsp;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) metal–semiconductor barrier diode, commonly known as a [[Schottky diode]]. This is included in the table because some silicon power IGFETs have a ''[[parasitic structure|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===
{{See also|Semiconductor package|Chip carrier}}
[[File:Transbauformen.jpg|thumb|Assorted discrete transistors]]
 
'''Discrete transistors''' are individually packaged transistors. Transistors come in many different [[semiconductor packages]] (see image). The two main categories are ''[[through-hole technology|through-hole]]'' (or ''leaded''), and ''surface-mount'', also known as ''surface-mount device'' ([[surface-mount technology|SMD]]). The ''ball grid array'' ([[Ball grid array|BGA]]) is the latest surface-mount package (currently only for large integrated circuits). 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]]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).
 
==See also==
{{Portal|Electronics}}
{{div col|colwidth=20em}}
*[[Band gap]]
*[[Digital electronics]]
*[[Moore's law]]
*[[Semiconductor device modeling]]
*[[Transistor count]]
*[[Transistor model]]
*[[Transresistance]]
*[[Very-large-scale integration]]
{{div col end}}
 
==Directory of external websites with datasheets==
* [http://www.onsemi.com/pub/Collateral/2N3903-D.PDF 2N3904]/[http://www.onsemi.com/pub/Collateral/2N3906-D.PDF 2N3906], [http://www.onsemi.com/pub/Collateral/BC182-D.PDF BC182]/[http://www.onsemi.com/pub/Collateral/BC212-D.PDF BC212] and [http://www.onsemi.com/pub/Collateral/BC546-D.PDF BC546]/[http://www.onsemi.com/pub/Collateral/BC556B-D.PDF 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]]: Germanium, 0.5 watt, 250&nbsp;MHz p–n–p BJT.
*BFP183: Low-power, 8&nbsp;GHz microwave n–p–n BJT.
* [http://www.national.com/ds/LM/LM194.pdf LM394]: "supermatch pair", with two n–p–n BJTs on a single substrate.
* [http://www.st.com/stonline/books/pdf/docs/9288.pdf 2N2219A]/[http://www.st.com/stonline/books/pdf/docs/9037.pdf 2N2905A]: BJT, general purpose, medium power, complementary pair. With metal cases they are rated at about one watt.
* [http://www.onsemi.com/pub/Collateral/2N3055-D.PDF 2N3055]/[http://www.onsemi.com/pub/Collateral/2N3055-D.PDF MJ2955]: For years, the n–p–n 2N3055 has been the "standard" power transistor. Its complement, the p–n–p MJ2955 arrived later. These 1&nbsp;MHz, 15 A, 60 V, 115 W BJTs are used in audio-power amplifiers, power supplies, and control.
* 2SC3281/2SA1302: Made by [[Toshiba]], these BJTs have low-distortion characteristics and are used in high-power audio amplifiers. They have been widely counterfeited [http://sound.westhost.com/counterfeit.htm].
* [http://www.st.com/stonline/books/pdf/docs/4491.pdf BU508]: n–p–n, 1500 V power BJT. Designed for [[television]] horizontal deflection, its high voltage capability also makes it suitable for use in ignition systems.
* [http://www.onsemi.com/pub/Collateral/MJ11012-D.PDF MJ11012/MJ11015]: 30 A, 120 V, 200 W, high power Darlington complementary pair BJTs. Used in audio amplifiers, control, and power switching.
* [http://www.fairchildsemi.com/ds/2N%2F2N5457.pdf 2N5457]/[http://www.fairchildsemi.com/ds/2N%2F2N5460.pdf 2N5460]: [[JFET]] (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.
* [http://www.irf.com/product-info/datasheets/data/irf3710.pdf IRF3710]/[http://www.irf.com/product-info/datasheets/data/irf5210.pdf IRF5210]: [[IGFET]] (enhancement mode), 40 A, 100 V, 200 W, near complementary pair.  For high-power amplifiers and power switches, especially in automobiles.
 
==References==
{{reflist|30em}}
 
==Further reading==
*{{cite book|author=Amos S W & James M R|title=Principles of Transistor Circuits|publisher=Butterworth-Heinemann|year=1999|isbn=0-7506-4427-3}}
*{{cite journal|author=Bacon, W. Stevenson|year=1968|title=The Transistor's 20th Anniversary: How Germanium And A Bit of Wire Changed The World|url=http://books.google.com/?id=mykDAAAAMBAJ&printsec=frontcover|journal=Bonnier Corp.: Popular Science, retrieved from [[Google Books]] 2009-03-22|volume=192|issue=6|pages=80–84|issn=0161-7370|publisher=Bonnier Corporation}}
*{{cite book|author=[[Paul Horowitz|Horowitz, Paul]] & Hill, Winfield|title=The Art of Electronics|publisher=Cambridge University Press|year=1989|isbn=0-521-37095-7}}
*{{cite book|author=Riordan, Michael & Hoddeson, Lillian|title=Crystal Fire|publisher=W.W Norton & Company Limited|year=1998|isbn=0-393-31851-6}} The invention of the transistor & the birth of the information age
*{{cite book|author=Warnes, Lionel|title=Analogue and Digital Electronics|publisher=Macmillan Press Ltd|year=1998|isbn=0-333-65820-5}}
*{{cite news|title=Herbert F. Mataré, An Inventor of the Transistor has his moment|date=24 February 2003|publisher=The New York Times|url=http://www.mindfully.org/Technology/2003/Transistor-Matare-Inventor24feb03.htm}}
*{{cite journal|author=Michael Riordan|year=2005|title=How Europe Missed the Transistor|journal=IEEE Spectrum|volume=42|issue=11|pages=52–57|url=http://spectrum.ieee.org/print/2155|doi=10.1109/MSPEC.2005.1526906}}
*{{cite book|author=C. D. Renmore|year=1980|title=Silicon Chips and You|isbn=0-8253-0022-3}}
*{{cite book|author=Wiley-IEEE Press|title=Complete Guide to Semiconductor Devices, 2nd Edition}}
 
==External links==
{{Wikibooks|Transistors}}
{{Commons category|Transistors}}
* [http://www.ck722museum.com/ ''The CK722 Museum]''. Website devoted to the "classic" hobbyist germanium transistor
* [http://www.ee.washington.edu/circuit_archive/parts/cross.html ''Jerry Russell's Transistor Cross Reference Database]''.
* [http://www.datasheetarchive.com/ ''The DatasheetArchive]''. Searchable database of transistor specifications and datasheets.
*[http://nobelprize.org/educational_games/physics/transistor/function/index.html The Transistor] Educational content from Nobelprize.org
*[http://news.bbc.co.uk/2/hi/technology/7091190.stm BBC: Building the digital age] photo history of transistors
*[http://www.porticus.org/bell/belllabs_transistor.html The Bell Systems Memorial on Transistors]
*[http://www.ieeeghn.org/wiki/index.php/The_Transistor_and_Portable_Electronics ''IEEE Global History Network, The Transistor and Portable Electronics'']. All about the history of transistors and integrated circuits.
*[http://www.pbs.org/transistor/ ''Transistorized]''. Historical and technical information from the [[Public Broadcasting Service]]
*[http://www.aps.org/publications/apsnews/200011/history.cfm ''This Month in Physics History: November 17 to December 23, 1947: Invention of the First Transistor]''. From the [[American Physical Society]]
*[http://www.sciencefriday.com/pages/1997/Dec/hour1_121297.html ''50 Years of the Transistor]''. From [[Science Friday]], December 12, 1997
*Charts showing many characteristics and giving direct access to most datasheets for [http://www.classiccmp.org/rtellason/transistors-2n.html 2N], [http://www.classiccmp.org/rtellason/transistors-2sa.html 2SA], [http://www.classiccmp.org/rtellason/transistors-2sb.html 2SB]. [http://www.classiccmp.org/rtellason/transistors-2sc.html 2SC], [http://www.classiccmp.org/rtellason/transistors-2sd.html 2SD], [http://www.classiccmp.org/rtellason/transistors-2sh-k.html 2SH-K], and [http://www.classiccmp.org/rtellason/transistors-3up.html other] numbers.
*[http://hamradio.lakki.iki.fi/new/Datasheets/transistor_pinouts/ Common transistor pinouts]
 
{{Electronic components}}
 
[[Category:Transistors|*]]
[[Category:American inventions]]
[[Category:Semiconductor devices]]
[[Category:1947 introductions]]
 
{{Link GA|de}}
{{Link GA|frr}}

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