Transistor

For other uses, see Transistor (disambiguation).A transistor is a semiconductor device used to amplify

Assorted discrete transistors. Packages in order from top to bot-tom: TO-3, TO-126, TO-92, SOT-23

and switch electronic signals and electrical power. It iscomposed of semiconductor material with at least threeterminals for connection to an external circuit. A voltageor current applied to one pair of the transistor’s terminalschanges the current through another pair of terminals.Because the controlled (output) power can be higher thanthe controlling (input) power, a transistor can amplify asignal. Today, some transistors are packaged individu-ally, but many more are found embedded in integratedcircuits.The transistor is the fundamental building block of mod-ern electronic devices, and is ubiquitous in modern elec-tronic systems. Following its development in 1947by American physicists John Bardeen, Walter Brattain,and William Shockley, the transistor revolutionized thefield of electronics, and paved the way for smaller andcheaper radios, calculators, and computers, among otherthings. The transistor is on the list of IEEE milestones inelectronics,[1] and the inventors were jointly awarded the1956 Nobel Prize in Physics for their achievement.[2]

1 History

Main article: History of the transistorThe thermionic triode, a vacuum tube invented in 1907

A replica of the first working transistor.

enabled amplified radio technology and long-distancetelephony. The triode, however, was a fragile device thatconsumed a lot of power. Physicist Julius Edgar Lilien-feld filed a patent for a field-effect transistor (FET) inCanada in 1925, which was intended to be a solid-statereplacement for the triode.[3][4] Lilienfeld also filed iden-tical patents in the United States in 1926[5] and 1928.[6][7]However, Lilienfeld did not publish any research articlesabout his devices nor did his patents cite any specific ex-amples of a working prototype. Because the productionof high-quality semiconductor materials was still decadesaway, Lilienfeld’s solid-state amplifier ideas would nothave found practical use in the 1920s and 1930s, even ifsuch a device had been built.[8] In 1934, German inventorOskar Heil patented a similar device.[9]

From November 17, 1947 to December 23, 1947, JohnBardeen and Walter Brattain at AT&T's Bell Labs in theUnited States, performed experiments and observed thatwhen two gold point contacts were applied to a crys-tal of germanium, a signal was produced with the out-put power greater than the input.[10] Solid State PhysicsGroup leader William Shockley saw the potential in this,and over the next few months worked to greatly expandthe knowledge of semiconductors. The term transis-tor was coined by John R. Pierce as a contraction ofthe term transresistance.[11][12][13] According to Lillian

1

2 2 IMPORTANCE

John Bardeen, William Shockley and Walter Brattain at BellLabs, 1948.

Hoddeson and Vicki Daitch, authors of a biography ofJohn Bardeen, Shockley had proposed that Bell Labs’ firstpatent for a transistor should be based on the field-effectand that he be named as the inventor. Having unearthedLilienfeld’s patents that went into obscurity years ear-lier, lawyers at Bell Labs advised against Shockley’s pro-posal because the idea of a field-effect transistor that usedan electric field as a “grid” was not new. Instead, whatBardeen, Brattain, and Shockley invented in 1947 wasthe first point-contact transistor.[8] In acknowledgementof this accomplishment, Shockley, Bardeen, and Brattainwere jointly awarded the 1956Nobel Prize in Physics “fortheir researches on semiconductors and their discovery ofthe transistor effect.”[14]

In 1948, the point-contact transistor was independentlyinvented by German physicists Herbert Mataré andHeinrich Welker while working at the Compagnie desFreins et Signaux, a Westinghouse subsidiary locatedin Paris. Mataré had previous experience in develop-ing crystal rectifiers from silicon and germanium in theGerman radar effort during World War II. Using thisknowledge, he began researching the phenomenon of"interference" in 1947. By June 1948, witnessing cur-rents flowing through point-contacts, Mataré producedconsistent results using samples of germanium producedby Welker, similar to what Bardeen and Brattain had ac-complished earlier in December 1947. Realizing thatBell Labs’ scientists had already invented the transistorbefore them, the company rushed to get its “transistron”into production for amplified use in France’s telephonenetwork.[15]

The first high-frequency transistor was the surface-barriergermanium transistor developed by Philco in 1953, ca-pable of operating up to 60 MHz.[16] These were madeby etching depressions into an N-type germanium basefrom both sides with jets of Indium(III) sulfate until itwas a few ten-thousandths of an inch thick. Indium elec-troplated into the depressions formed the collector andemitter.[17][18] The first all-transistor car radio, which was

Philco surface-barrier transistor developed and produced in1953

produced in 1955 byChrysler and Philco, used these tran-sistors in its circuitry and also they were the first suitablefor high-speed computers.[19][20][21][22]

The first working silicon transistor was developed at BellLabs on January 26, 1954 by Morris Tanenbaum.[23] Thefirst commercial silicon transistor was produced by TexasInstruments in 1954.[24] This was the work of GordonTeal, an expert in growing crystals of high purity, whohad previously worked at Bell Labs.[25] The first MOStransistor actually built was by Kahng and Atalla at BellLabs in 1960.[26]

2 Importance

The transistor is the key active component in practicallyall modern electronics. Many consider it to be one of thegreatest inventions of the 20th century.[27] Its importancein today’s society rests on its ability to be mass-producedusing a highly automated process (semiconductor devicefabrication) that achieves astonishingly low per-transistorcosts. The invention of the first transistor at Bell Labs wasnamed an IEEE Milestone in 2009.[28]

Although several companies each produce over a billionindividually packaged (known as discrete) transistors ev-ery year,[29] the vast majority of transistors are now pro-duced in integrated circuits (often shortened to IC, mi-crochips or simply chips), along with diodes, resistors,capacitors and other electronic components, to producecomplete electronic circuits. A logic gate consists of upto about twenty transistors whereas an advanced micro-processor, as of 2009, can use as many as 3 billion transis-tors (MOSFETs).[30] “About 60 million transistors were

3.1 Transistor as a switch 3

A Darlington transistor opened up so the actual transistor chip(the small square) can be seen inside. A Darlington transistoris effectively two transistors on the same chip. One transistor ismuch larger than the other, but both are large in comparison totransistors in large-scale integration because this particular ex-ample is intended for power applications.

built in 2002 ... for [each] man, woman, and child onEarth.”[31]

The transistor’s low cost, flexibility, and reliability havemade it a ubiquitous device. Transistorized mechatroniccircuits have replaced electromechanical devices in con-trolling appliances and machinery. It is often easier andcheaper to use a standard microcontroller and write acomputer program to carry out a control function thanto design an equivalent mechanical control function.

3 Simplified operation

base

collector

emitter

VOUT

VIN

VCC

A simple circuit diagram to show the labels of a n–p–n bipolartransistor.

The essential usefulness of a transistor comes from itsability to use a small signal applied between one pair of its

terminals to control a much larger signal at another pairof terminals. This property is called gain. It can producea stronger output signal, a voltage or current, that is pro-portional to a weaker input signal; that is, it can act asan amplifier. Alternatively, the transistor can be used toturn current on or off in a circuit as an electrically con-trolled switch, where the amount of current is determinedby other circuit elements.There are two types of transistors, which have slight dif-ferences in how they are used in a circuit. A bipolar tran-sistor has terminals labeled base, collector, and emitter.A small current at the base terminal (that is, flowing be-tween the base and the emitter) can control or switch amuch larger current between the collector and emitter ter-minals. For a field-effect transistor, the terminals are la-beled gate, source, and drain, and a voltage at the gatecan control a current between source and drain.The image to the right represents a typical bipolar tran-sistor in a circuit. Charge will flow between emitter andcollector terminals depending on the current in the base.Because internally the base and emitter connections be-have like a semiconductor diode, a voltage drop developsbetween base and emitter while the base current exists.The amount of this voltage depends on the material thetransistor is made from, and is referred to as VBE.

3.1 Transistor as a switch

+ 6 V

1 k

IBE

ICE

BJT used as an electronic switch, in grounded-emitter configura-tion.

Transistors are commonly used as electronic switches,both for high-power applications such as switched-modepower supplies and for low-power applications such aslogic gates.In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the emitterand collector currents rise exponentially. The collectorvoltage drops because of reduced resistance from collec-tor to emitter. If the voltage difference between the col-lector and emitter were zero (or near zero), the collectorcurrent would be limited only by the load resistance (light

4 4 COMPARISON WITH VACUUM TUBES

bulb) and the supply voltage. This is called saturation be-cause current is flowing from collector to emitter freely.When saturated, the switch is said to be on.[32]

Providing sufficient base drive current is a key problem inthe use of bipolar transistors as switches. The transistorprovides current gain, allowing a relatively large currentin the collector to be switched by a much smaller cur-rent into the base terminal. The ratio of these currentsvaries depending on the type of transistor, and even for aparticular type, varies depending on the collector current.In the example light-switch circuit shown, the resistor ischosen to provide enough base current to ensure the tran-sistor will be saturated.In any switching circuit, values of input voltage would bechosen such that the output is either completely off,[33] orcompletely on. The transistor is acting as a switch, andthis type of operation is common in digital circuits whereonly “on” and “off” values are relevant.

3.2 Transistor as an amplifier

B C

E

V

V

V R

R

R

R

C

C

C

+

in

out C

E

1

2

in

out

E

Amplifier circuit, common-emitter configuration with a voltage-divider bias circuit.

The common-emitter amplifier is designed so that a smallchange in voltage (V ᵢ ) changes the small current throughthe base of the transistor; the transistor’s current amplifi-cation combined with the properties of the circuit meanthat small swings in V ᵢ produce large changes in Vₒᵤ .Various configurations of single transistor amplifier arepossible, with some providing current gain, some voltagegain, and some both.Frommobile phones to televisions, vast numbers of prod-ucts include amplifiers for sound reproduction, radio

transmission, and signal processing. The first discrete-transistor audio amplifiers barely supplied a few hun-dred milliwatts, but power and audio fidelity graduallyincreased as better transistors became available and am-plifier architecture evolved.Modern transistor audio amplifiers of up to a few hundredwatts are common and relatively inexpensive.

4 Comparison with vacuum tubes

Prior to the development of transistors, vacuum (elec-tron) tubes (or in the UK “thermionic valves” or just“valves”) were the main active components in electronicequipment.

4.1 Advantages

The key advantages that have allowed transistors to re-place their vacuum tube predecessors in most applica-tions are

• No power consumption by a cathode heater; thecharacteristic orange glow of vacuum tubes is dueto a simple electrical heating element, much like alight bulb filament.

• Small size and minimal weight, allowing the devel-opment of miniaturized electronic devices.

• Low operating voltages compatible with batteries ofonly a few cells.

• No warm-up period for cathode heaters required af-ter power application.

• Lower power dissipation and generally greater en-ergy efficiency.

• Higher reliability and greater physical ruggedness.

• Extremely long life. Some transistorized deviceshave been in service for more than 50 years.

• Complementary devices available, facilitating thedesign of complementary-symmetry circuits, some-thing not possible with vacuum tubes.

• Greatly reduced sensitivity to mechanical shockand vibration, thus reducing the problem ofmicrophonics in sensitive applications, such as au-dio.

4.2 Limitations

• Silicon transistors can age and fail.[34]

5.1 Bipolar junction transistor (BJT) 5

• High-power, high-frequency operation, such as thatused in over-the-air television broadcasting, is betterachieved in vacuum tubes due to improved electronmobility in a vacuum.

• Solid-state devices are more vulnerable toelectrostatic discharge in handling and opera-tion

• A vacuum tubemomentarily overloaded will just geta little hotter; solid-state devices have less mass toabsorb the heat due to overloads, in proportion totheir rating

• Sensitivity to radiation and cosmic rays (specialradiation-hardened chips are used for spacecraft de-vices).

• Vacuum tubes create a distortion, the so-called tubesound, which some people find to be more tolerableto the ear.[35]

5 Types

BJT and JFET symbolsJFET and IGFET symbols

Transistors are categorized by

• Semiconductor material (date first used): themetalloids germanium (1947) and silicon (1954)—in amorphous, polycrystalline and monocrystallineform; the compounds gallium arsenide (1966) andsilicon carbide (1997), the alloy silicon-germanium(1989), the allotrope of carbon graphene (researchongoing since 2004), etc.—see Semiconductor ma-terial

• Structure: BJT, JFET, IGFET (MOSFET),insulated-gate bipolar transistor, “other types”

• Electrical polarity (positive and negative): n–p–n,p–n–p (BJTs); n-channel, p-channel (FETs)

• Maximum power rating: low, medium, high

• Maximum operating frequency: low, medium, high,radio (RF), microwave frequency (the maximum ef-fective frequency of a transistor is denoted by theterm fT , an abbreviation for transition frequency—the frequency of transition is the frequency at whichthe transistor yields unity gain)

• Application: switch, general purpose, audio, highvoltage, super-beta, matched pair

• Physical packaging: through-hole metal, through-hole plastic, surface mount, ball grid array, powermodules—see Packaging

• Amplification factor h ₑ, βF (transistor beta)[36] org (transconductance).

Thus, a particular transistor may be described as silicon,surface-mount, BJT, n–p–n, low-power, high-frequencyswitch.

5.1 Bipolar junction transistor (BJT)

Main article: Bipolar junction transistor

Bipolar transistors are so named because they conduct byusing both majority and minority carriers. The bipolarjunction transistor, the first type of transistor to be mass-produced, is a combination of two junction diodes, andis formed of either a thin layer of p-type semiconduc-tor sandwiched between two n-type semiconductors (ann–p–n transistor), or a thin layer of n-type semiconduc-tor sandwiched between two p-type semiconductors (ap–n–p transistor). This construction produces two p–njunctions: a base–emitter junction and a base–collectorjunction, separated by a thin region of semiconductorknown as the base region (two junction diodes wired to-gether without sharing an intervening semiconducting re-gion will not make a transistor).BJTs have three terminals, corresponding to the threelayers of semiconductor—an emitter, a base, and a col-lector. They are useful in amplifiers because the cur-rents at the emitter and collector are controllable by arelatively small base current.”[37] In an n–p–n transistoroperating in the active region, the emitter–base junctionis forward biased (electrons and holes recombine at thejunction), and electrons are injected into the base re-gion. Because the base is narrow, most of these elec-trons will diffuse into the reverse-biased (electrons andholes 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 recombinein the base, which is the dominant mechanism in the basecurrent. By controlling the number of electrons that canleave the base, the number of electrons entering the col-lector can be controlled.[37] Collector current is approx-imately β (common-emitter current gain) times the basecurrent. It is typically greater than 100 for small-signaltransistors but can be smaller in transistors designed forhigh-power applications.Unlike the field-effect transistor (see below), the BJT is alow–input-impedance device. Also, as the base–emittervoltage (Vbe) is increased the base–emitter current andhence the collector–emitter current (Ice) increase expo-nentially according to the Shockley diode model and theEbers-Moll model. Because of this exponential relation-ship, the BJT has a higher transconductance than the FET.Bipolar transistors can be made to conduct by exposureto light, because absorption of photons in the base regiongenerates a photocurrent that acts as a base current; the

6 5 TYPES

collector current is approximately β times the photocur-rent. Devices designed for this purpose have a transparentwindow in the package and are called phototransistors.

5.2 Field-effect transistor (FET)

Main articles: Field-effect transistor, MOSFET andJFET

The field-effect transistor, sometimes called a unipolartransistor, uses either electrons (in n-channel FET) orholes (in p-channel FET) for conduction. The four termi-nals of the FET are named source, gate, drain, and body(substrate). On most FETs, the body is connected to thesource inside the package, and this will be assumed forthe following description.In a FET, the drain-to-source current flows via a conduct-ing channel that connects the source region to the drain re-gion. The conductivity is varied by the electric field thatis produced when a voltage is applied between the gateand source terminals; hence the current flowing betweenthe drain and source is controlled by the voltage appliedbetween the gate and source. As the gate–source volt-age (Vgs) is increased, the drain–source current (Ids) in-creases exponentially forVgs below threshold, and then ata roughly quadratic rate ( Ids ∝ (Vgs−VT )

2 ) (whereVTis the threshold voltage at which drain current begins)[38]in the "space-charge-limited" region above threshold. Aquadratic behavior is not observed in modern devices, forexample, at the 65 nm technology node.[39]

For low noise at narrow bandwidth the higher input resis-tance of the FET is advantageous.FETs are divided into two families: junction FET (JFET)and insulated gate FET (IGFET). The IGFET is morecommonly known as a metal–oxide–semiconductor FET(MOSFET), reflecting its original construction from lay-ers of metal (the gate), oxide (the insulation), and semi-conductor. Unlike IGFETs, the JFET gate forms a p–ndiode with the channel which lies between the source anddrain. Functionally, this makes the n-channel JFET thesolid-state equivalent of the vacuum tube triode which,similarly, forms a diode between its grid and cathode.Also, both devices operate in the depletion mode, theyboth have a high input impedance, and they both conductcurrent under the control of an input voltage.Metal–semiconductor FETs (MESFETs) are JFETs inwhich the reverse biased p–n junction is replaced by ametal–semiconductor junction. These, and the HEMTs(high-electron-mobility transistors, or HFETs), in whicha two-dimensional electron gas with very high carrier mo-bility is used for charge transport, are especially suitablefor use at very high frequencies (microwave frequencies;several GHz).FETs are further divided into depletion-mode andenhancement-mode types, depending on whether the

channel is turned on or off with zero gate-to-source volt-age. For enhancement mode, the channel is off at zerobias, and a gate potential can “enhance” the conduction.For the depletion mode, the channel is on at zero bias, anda gate potential (of the opposite polarity) can “deplete”the channel, reducing conduction. For either mode, amore positive gate voltage corresponds to a higher currentfor n-channel devices and a lower current for p-channeldevices. Nearly all JFETs are depletion-mode becausethe diode junctions would forward bias and conduct ifthey were enhancement-mode devices; most IGFETs areenhancement-mode types.

5.3 Usage of bipolar and field-effect tran-sistors

The bipolar junction transistor (BJT) was the most com-monly used transistor in the 1960s and 70s. Even afterMOSFETs became widely available, the BJT remainedthe transistor of choice for many analog circuits such asamplifiers because of their greater linearity and ease ofmanufacture. In integrated circuits, the desirable prop-erties of MOSFETs allowed them to capture nearly allmarket share for digital circuits. Discrete MOSFETs canbe applied in transistor applications, including analog cir-cuits, voltage regulators, amplifiers, power transmittersand motor drivers.

5.4 Other transistor types

Transistor symbol drawn on Portuguese pavement in theUniversity of Aveiro.

For early bipolar transistors, see Bipolar junction tran-sistor#Bipolar transistors.

• Bipolar junction transistor

• Heterojunction bipolar transistor, up to sev-eral hundred GHz, common in modern ultra-fast and RF circuits

5.4 Other transistor types 7

• Schottky transistor• Avalanche transistor• Darlington transistors are two BJTs connectedtogether to provide a high current gain equalto the product of the current gains of the twotransistors.

• Insulated-gate bipolar transistors (IGBTs) usea medium-power IGFET, similarly connectedto a power BJT, to give a high inputimpedance. Power diodes are often connectedbetween certain terminals depending on spe-cific use. IGBTs are particularly suitable forheavy-duty industrial applications. The AseaBrown Boveri (ABB) 5SNA2400E170100 il-lustrates just how far power semiconduc-tor technology has advanced.[40] Intended forthree-phase power supplies, this device housesthree n–p–n IGBTs in a case measuring 38 by140 by 190 mm and weighing 1.5 kg. EachIGBT is rated at 1,700 volts and can handle2,400 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 asthe pickup of a record player or radio frontends. Effectively, it is a very large numberof transistors in parallel where, at the output,the signal is added constructively, but randomnoise is added only stochastically.[41]

• Field-effect transistor

• Carbon nanotube field-effect transistor (CN-FET)

• JFET, where the gate is insulated by a reverse-biased p–n junction

• MESFET, similar to JFET with a Schottkyjunction instead of a p–n junction• High-electron-mobility transistor(HEMT, HFET, MODFET)

• MOSFET, where the gate is insulated by ashallow layer of insulator

• Inverted-T field-effect transistor (ITFET)• FinFET, source/drain region shapes fins on thesilicon surface.

• FREDFET, fast-reverse epitaxial diode field-effect transistor

• Thin-film transistor, in LCDs.• Organic field-effect transistor (OFET), inwhich the semiconductor is an organic com-pound

• Ballistic transistor

• Floating-gate transistor, for non-volatile stor-age.

• FETs used to sense environment• Ion-sensitive field effect transistor (IF-SET), to measure ion concentrations insolution.

• EOSFET, electrolyte-oxide-semiconductor field-effect transistor(Neurochip)

• DNAFET, deoxyribonucleic acid field-effect transistor

• Tunnel field-effect transistor. TFETs switch bymodulating quantum tunnelling through a barrier.

• Diffusion transistor, formed by diffusing dopantsinto semiconductor substrate; can be both BJT andFET

• Unijunction transistors can be used as simple pulsegenerators. They comprise a main body of either P-type or N-type semiconductor with ohmic contactsat each end (terminals Base1 and Base2). A junctionwith the opposite semiconductor type is formed ata point along the length of the body for the thirdterminal (Emitter).

• Single-electron transistors (SET) consist of a gate is-land between two tunneling junctions. The tunnel-ing current is controlled by a voltage applied to thegate through a capacitor.[42]

• Nanofluidic transistor, controls the movementof ions through sub-microscopic, water-filledchannels.[43]

• Multigate devices

• Tetrode transistor• Pentode transistor• Trigate transistors (Prototype by Intel)• Dual-gate FETs have a single channel withtwo gates in cascode; a configuration opti-mized for high-frequency amplifiers, mixers,and oscillators.

• Junctionless nanowire transistor (JNT), uses a sim-ple nanowire of silicon surrounded by an electricallyisolated “wedding ring” that acts to gate the flow ofelectrons through the wire.

• Vacuum-channel transistor: In 2012, NASA and theNational Nanofab Center in South Korea were re-ported to have built a prototype vacuum-channeltransistor in only 150 nanometers in size, can bemanufactured cheaply using standard silicon semi-conductor processing, can operate at high speedseven in hostile environments, and could consumejust as much power as a standard transistor.[44]

• Organic electrochemical transistor

8 7 CONSTRUCTION

6 Part numbering standards / spec-ifications

The types of some transistors can be parsed from the partnumber. There are three major semiconductor namingstandards; in each the alphanumeric prefix provides cluesto type of the device.

6.1 Japanese Industrial Standard (JIS)

The JIS-C-7012 specification for transistor part numbersstarts with “2S”,[45] e.g. 2SD965, but sometimes the “2S”prefix is not marked on the package – a 2SD965 mightonly be marked “D965"; a 2SC1815 might be listed bya supplier as simply “C1815”. This series sometimes hassuffixes (such as “R”, “O”, “BL”... standing for “Red”,“Orange”, “Blue” etc.) to denote variants, such as tighterhFE (gain) groupings.

6.2 European Electronic ComponentManufacturers Association (EECA)

The Pro Electron standard, the European ElectronicComponent Manufacturers Association part numberingscheme, begins with two letters: the first gives the semi-conductor type (A for germanium, B for silicon, and Cfor materials like GaAs); the second letter denotes theintended use (A for diode, C for general-purpose tran-sistor, etc.). A 3-digit sequence number (or one letterthen 2 digits, for industrial types) follows. With early de-vices this indicated the case type. Suffixes may be used,with a letter (e.g. “C” often means high hFE, such as in:BC549C[46]) or other codes may follow to show gain (e.g.BC327-25) or voltage rating (e.g. BUK854-800A[47]).The more common prefixes are:

6.3 Joint Electron Devices EngineeringCouncil (JEDEC)

The JEDEC EIA370 transistor device numbers usuallystart with “2N”, indicating a three-terminal device (dual-gate field-effect transistors are four-terminal devices, sobegin with 3N), then a 2, 3 or 4-digit sequential num-ber with no significance as to device properties (althoughearly 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. Aletter suffix (such as “A”) is sometimes used to indicate anewer variant, but rarely gain groupings.

6.4 Proprietary

Manufacturers of devices may have their own proprietarynumbering system, for example CK722. Since devices

are second-sourced, a manufacturer’s prefix (like “MPF”in MPF102, which originally would denote a MotorolaFET) now is an unreliable indicator of who made thedevice. Some proprietary naming schemes adopt partsof other naming schemes, for example a PN2222A is a(possibly Fairchild Semiconductor) 2N2222A in a plas-tic case (but a PN108 is a plastic version of a BC108, nota 2N108, while the PN100 is unrelated to other xx100devices).Military part numbers sometimes are assigned their owncodes, such as the British Military CV Naming System.Manufacturers buying large numbers of similar parts mayhave them supplied with “house numbers”, identifyinga particular purchasing specification and not necessar-ily a device with a standardized registered number. Forexample, an HP part 1854,0053 is a (JEDEC) 2N2218transistor[48][49] which is also assigned the CV number:CV7763[50]

6.5 Naming problems

With so many independent naming schemes, and the ab-breviation of part numbers when printed on the devices,ambiguity sometimes occurs. For example two differentdevices may be marked “J176” (one the J176 low-powerJunction FET, the other the higher-powered MOSFET2SJ176).As older “through-hole” transistors are given surface-mount packaged counterparts, they tend to be assignedmany different part numbers because manufacturers havetheir own systems to cope with the variety in pinout ar-rangements 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 stan-dards authority, and well known by engineers over theyears, the new versions are far from standardized in theirnaming.

7 Construction

7.1 Semiconductor material

The first BJTs were made from germanium (Ge). Silicon(Si) types currently predominate but certain advancedmicrowave and high-performance versions now employthe compound semiconductor material gallium arsenide(GaAs) and the semiconductor alloy silicon germanium(SiGe). Single element semiconductor material (Ge andSi) is described as elemental.Rough parameters for the most common semiconductormaterials used to make transistors are given in the table tothe right; these parameters will vary with increase in tem-perature, electric field, impurity level, strain, and sundryother factors.

7.2 Packaging 9

The junction forward voltage is the voltage applied to theemitter–base junction of a BJT in order to make the baseconduct a specified current. The current increases ex-ponentially as the junction forward voltage is increased.The values given in the table are typical for a current of1 mA (the same values apply to semiconductor diodes).The lower the junction forward voltage the better, as thismeans that less power is required to “drive” the transis-tor. The junction forward voltage for a given current de-creases with increase in temperature. For a typical siliconjunction the change is −2.1 mV/°C.[51] In some circuitsspecial compensating elements (sensistors) must be usedto compensate for such changes.The density of mobile carriers in the channel of a MOS-FET is a function of the electric field forming the chan-nel and of various other phenomena such as the impuritylevel in the channel. Some impurities, called dopants, areintroduced deliberately in making a MOSFET, to controlthe MOSFET electrical behavior.The electron mobility and hole mobility columns show theaverage speed that electrons and holes diffuse through thesemiconductor material with an electric field of 1 volt permeter applied across the material. In general, the higherthe electron mobility the faster the transistor can operate.The table indicates that Ge is a better material than Si inthis respect. However, Ge has four major shortcomingscompared to silicon and gallium arsenide:

• Its maximum temperature is limited;

• it has relatively high leakage current;

• it cannot withstand high voltages;

• it is less suitable for fabricating integrated circuits.

Because the electron mobility is higher than the hole mo-bility 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 ofthe three semiconductors. It is for this reason that GaAsis used in high-frequency applications. A relatively re-cent FET development, the high-electron-mobility tran-sistor (HEMT), has a heterostructure (junction betweendifferent semiconductor materials) of aluminium gal-lium arsenide (AlGaAs)-gallium arsenide (GaAs) whichhas twice the electron mobility of a GaAs-metal barrierjunction. Because of their high speed and low noise,HEMTs are used in satellite receivers working at frequen-cies around 12 GHz. HEMTs based on gallium nitrideand aluminium gallium nitride (AlGaN/GaN HEMTs)provide a still higher electron mobility and are being de-veloped for various applications.Max. junction temperature values represent a crosssection taken from various manufacturers’ data sheets.This temperature should not be exceeded or the transistormay be damaged.

Al–Si junction refers to the high-speed (aluminum–silicon) metal–semiconductor barrier diode, commonlyknown as a Schottky diode. This is included in the ta-ble because some silicon power IGFETs have a parasiticreverse Schottky diode formed between the source anddrain as part of the fabrication process. This diode canbe a nuisance, but sometimes it is used in the circuit.

7.2 Packaging

See also: Semiconductor package and Chip carrierDiscrete transistors are individually packaged transis-

Assorted discrete transistors

tors. Transistors come in many different semiconductorpackages (see image). The two main categories arethrough-hole (or leaded), and surface-mount, also knownas surface-mount device (SMD). The ball grid array(BGA) is the latest surface-mount package (currently onlyfor large integrated circuits). It has solder “balls” on theunderside in place of leads. Because they are smaller andhave shorter interconnections, SMDs have better high-frequency characteristics but lower power rating.Transistor packages are made of glass, metal, ceramic, orplastic. The package often dictates the power rating andfrequency characteristics. Power transistors have largerpackages that can be clamped to heat sinks for enhancedcooling. Additionally, most power transistors have thecollector or drain physically connected to the metal en-closure. At the other extreme, some surface-mount mi-crowave transistors are as small as grains of sand.Often a given transistor type is available in several pack-ages. Transistor packages are mainly standardized, butthe assignment of a transistor’s functions to the terminalsis not: other transistor types can assign other functionsto the package’s terminals. Even for the same transis-tor type the terminal assignment can vary (normally indi-cated by a suffix letter to the part number, q.e. BC212Land BC212K).Nowadays most transistors come in a wide range of SMTpackages, in comparison the list of available through-holepackages is relatively small, here is a short list of themost common through-hole transistors packages in alpha-betical order: ATV, E-line, MRT, HRT, SC-43, SC-72,TO-3, TO-18, TO-39, TO-92, TO-126, TO220, TO247,

10 10 REFERENCES

TO251, TO262, ZTX851

7.2.1 Flexible transistors

Researchers have made several kinds of flexible tran-sistors, including organic field-effect transistors.[52][53][54]Flexible transistors are useful in some kinds of flexibledisplays and other flexible electronics.

8 See also• Band gap

• Digital electronics

• Moore’s law

• Semiconductor device modeling

• Transistor count

• Transistor model

• Transresistance

• Very-large-scale integration

9 Directory of external websiteswith datasheets

• 2N3904/2N3906, BC182/BC212 andBC546/BC556: Ubiquitous, BJT, general-purpose,low-power, complementary pairs. They have plasticcases and cost roughly ten cents U.S. in smallquantities, making them popular with hobbyists.

• AF107: Germanium, 0.5 watt, 250 MHz p–n–pBJT.

• BFP183: Low-power, 8 GHz microwave n–p–nBJT.

• LM394: “supermatch pair”, with two n–p–n BJTson a single substrate.

• 2N2219A/2N2905A: BJT, general purpose,medium power, complementary pair. With metalcases they are rated at about one watt.

• 2N3055/MJ2955: For years, the n–p–n 2N3055 hasbeen the “standard” power transistor. Its comple-ment, the p–n–p MJ2955 arrived later. These 1MHz, 15 A, 60 V, 115 W BJTs are used in audio-power amplifiers, power supplies, and control.

• 2SC3281/2SA1302: Made by Toshiba, these BJTshave low-distortion characteristics and are used inhigh-power audio amplifiers. They have been widelycounterfeited .

• BU508: n–p–n, 1500 V power BJT. Designed fortelevision horizontal deflection, its high voltage ca-pability also makes it suitable for use in ignition sys-tems.

• MJ11012/MJ11015: 30 A, 120 V, 200 W, highpower Darlington complementary pair BJTs. Usedin audio amplifiers, control, and power switching.

• 2N5457/2N5460: JFET (depletion mode), generalpurpose, low power, complementary pair.

• BSP296/BSP171: IGFET (enhancement mode),medium power, near complementary pair. Used forlogic level conversion and driving power transistorsin amplifiers.

• IRF3710/IRF5210: IGFET (enhancement mode),40 A, 100 V, 200 W, near complementary pair.For high-power amplifiers and power switches, es-pecially in automobiles.

10 References[1] "Milestones:Invention of the First Transistor at Bell Tele-

phone Laboratories, Inc., 1947”. IEEE Global HistoryNetwork. IEEE. Retrieved 7 December 2014.

[2] “TheNobel Prize in Physics 1956”. Nobelprize.org. NobelMedia AB. Retrieved 7 December 2014.

[3] Vardalas, John, Twists and Turns in the Development ofthe Transistor IEEE-USA Today’s Engineer, May 2003.

[4] Lilienfeld, Julius Edgar, “Method and apparatus for con-trolling electric current” U.S. Patent 1,745,175 January28, 1930 (filed in Canada 1925-10-22, in US 1926-10-08).

[5] “Method And Apparatus For Controlling Electric Cur-rents”. United States Patent and Trademark Office.

[6] “Amplifier For Electric Currents”. United States Patentand Trademark Office.

[7] “Device For Controlling Electric Current”. United StatesPatent and Trademark Office.

[8] “Twists and Turns in the Development of the Transistor”.Institute of Electrical and Electronics Engineers, Inc.

[9] Heil, Oskar, “Improvements in or relating to electricalamplifiers and other control arrangements and devices”,Patent No. GB439457, European Patent Office, filed inGreat Britain 1934-03-02, published December 6, 1935(originally filed in Germany 1934-03-02).

[10] “November 17 – December 23, 1947: Invention of theFirst Transistor”. American Physical Society.

[11] Bell Laboratories (1983). S. Millman, ed. A History ofEngineering and Science in the Bell System, Physical Sci-ence (1925-1980). AT&T Bell Laboratories. p. 102.

11

[12] David Bodanis (2005). Electric Universe. Crown Publish-ers, New York. ISBN 0-7394-5670-9.

[13] “transistor”. American Heritage Dictionary (3rd ed.).Boston: Houghton Mifflin. 1992.

[14] “The Nobel Prize in Physics 1956”.

[15] “1948 - The European Transistor Invention”. ComputerHistory Museum.

[16] Proceeding of the IRE, Dec 1953, Author: W.E. Bradley- Philco Corp.,Research Division, Volume 41 issue 12,pages 1702-1706

[17] Wall Street Journal, December 4, 1953, page 4, Article“Philco Claims Its Transistor Outperforms Others Now InUse”

[18] Electronics magazine, January 1954, Article “Electro-plated Transistors Announced”

[19] Wall Street Journal, “Chrysler Promises Car Radio WithTransistors Instead of Tubes in '56”, April 28, 1955, page1

[20] Los Angeles Times, May 8, 1955, page A20, Article:“Chrysler Announces New Transistor Radio”

[21] Philco TechRep Division Bulletin, May–June 1955, Vol-ume 5 Number 3, page 28

[22] Saul Rosen (Jun 1991). PHILCO: Some Recollectionsof the PHILCO TRANSAC S-2000 (Computer ScienceTechnical Reports / Purdue e-Pubs) (CSD-TR-91-051).Purdue University. Here: page 2

[23] IEEE Spectrum, The Lost History of the Transistor, Au-thor: Michael Riordan, May 2004, pp 48-49

[24] 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.

[25] Grant McFarland, Microprocessor design: a practicalguide from design planning to manufacturing, p.10,McGraw-Hill Professional, 2006 ISBN 0-07-145951-0.

[26] W. Heywang, K. H. Zaininger, “Silicon: The Semi-conductor Material”, Silicon: evolution and future of atechnology (Editors: P. Siffert, E. F. Krimmel), p.36,Springer, 2004 ISBN 3-540-40546-1.

[27] RobertW. Price (2004). Roadmap to Entrepreneurial Suc-cess. AMACOMDivAmericanMgmtAssn. p. 42. ISBN978-0-8144-7190-6.

[28] "Milestones:Invention of the First Transistor at Bell Tele-phone Laboratories, Inc., 1947”. IEEE Global HistoryNetwork. IEEE. Retrieved August 3, 2011.

[29] FETs/MOSFETs: Smaller apps push up surface-mountsupply

[30] "ATI and Nvidia face off.” October 7, 2009. Retrieved onFebruary 2, 2011.

[31] Jim Turley. “The Two Percent Solution” 2002.

[32] Kaplan, Daniel (2003). Hands-On Electronics. NewYork:Cambridge University Press. pp. 47–54, 60–61. ISBN978-0-511-07668-8.

[33] apart from a small value due to leakage currents

[34] John Keane and Chris H. Kim, “Transistor Aging,” IEEESpectrum (web feature), April 25, 2011.

[35] van der Veen, M. (2005). “Universal system and outputtransformer for valve amplifiers” (PDF). 118th AES Con-vention, Barcelona, Spain.

[36] “Transistor Example”. 071003 bcae1.com

[37] Streetman, Ben (1992). Solid State Electronic Devices.Englewood Cliffs, NJ: Prentice-Hall. pp. 301–305. ISBN0-13-822023-9.

[38] Horowitz, Paul; Winfield Hill (1989). The Art of Electron-ics (2nd ed.). Cambridge University Press. p. 115. ISBN0-521-37095-7.

[39] W. M. C. Sansen (2006). Analog design essentials. NewYork ; Berlin: Springer. p. §0152, p. 28. ISBN 0-387-25746-2.

[40] “IGBT Module 5SNA 2400E170100” (PDF). RetrievedJune 30, 2012.

[41] Zhong Yuan Chang, Willy M. C. Sansen, Low-NoiseWide-Band Amplifiers in Bipolar and CMOS Technologies,page 31, Springer, 1991 ISBN 0792390962.

[42] “Single Electron Transistors”. Snow.stanford.edu. Re-trieved June 30, 2012.

[43] Sanders, Robert (June 28, 2005). “Nanofluidic transistor,the basis of future chemical processors”. Berkeley.edu.Retrieved June 30, 2012.

[44] The return of the vacuum tube?

[45] “Clive TEC Transistors Japanese Industrial Standards”.Clivetec.0catch.com. Retrieved June 30, 2012.

[46] “Datasheet for BC549, with A,B and C gain groupings”(PDF). Retrieved June 30, 2012.

[47] “Datasheet for BUK854-800A (800volt IGBT)" (PDF).Retrieved June 30, 2012.

[48] “Richard Freeman’s HP Part numbers Crossreference”.Hpmuseum.org. Retrieved June 30, 2012.

[49] Transistor–Diode Cross Reference – H.P. Part Numbersto JEDEC (pdf)

[50] “CVDevice Cross-reference byAndy Lake”. Qsl.net. Re-trieved June 30, 2012.

[51] A.S. Sedra and K.C. Smith (2004). Microelectronic cir-cuits (Fifth ed.). New York: Oxford University Press. pp.397 and Figure 5.17. ISBN 0-19-514251-9.

[52] Jhonathan P. Rojas, Galo A. Torres Sevilla, and Muham-mad M. Hussain. “Can We Build a Truly High Perfor-mance Computer Which is Flexible and Transparent?".

12 12 EXTERNAL LINKS

[53] Kan Zhang, Jung-Hun Seo1, Weidong Zhou and Zhen-qiang Ma. “Fast flexible electronics using transferrablesilicon nanomembranes”. 2012.

[54] Lisa Zyga. “Carbon nanotube transistors could lead to in-expensive, flexible electronics”. 2011.

11 Further reading

• Amos SW&JamesMR (1999). Principles of Tran-sistor Circuits. Butterworth-Heinemann. ISBN 0-7506-4427-3.

• Bacon, W. Stevenson (1968). “The Transistor’s20th Anniversary: How Germanium And A Bit ofWire Changed The World”. Bonnier Corp.: Popu-lar Science, retrieved from Google Books 2009-03-22 (Bonnier Corporation) 192 (6): 80–84. ISSN0161-7370.

• Horowitz, Paul & Hill, Winfield (1989). The Art ofElectronics. Cambridge University Press. ISBN 0-521-37095-7.

• Riordan, Michael & Hoddeson, Lillian (1998).Crystal Fire. W.W Norton & Company Limited.ISBN 0-393-31851-6. The invention of the transis-tor & the birth of the information age

• Warnes, Lionel (1998). Analogue and Digital Elec-tronics. Macmillan Press Ltd. ISBN 0-333-65820-5.

• “Herbert F. Mataré, An Inventor of the Transistorhas his moment”. The New York Times. February24, 2003.

• Michael Riordan (2005). “How Europe Missedthe Transistor”. IEEE Spectrum 42 (11): 52–57.doi:10.1109/MSPEC.2005.1526906.

• C. D. Renmore (1980). Silicon Chips and You.ISBN 0-8253-0022-3.

• Wiley-IEEE Press. Complete Guide to Semiconduc-tor Devices, 2nd Edition.

12 External links

• The CK722Museum. Website devoted to the “classic”hobbyist germanium transistor

• The Transistor Educational content from Nobel-prize.org

• BBC: Building the digital age photo history of tran-sistors

• The Bell Systems Memorial on Transistors

• IEEE Global History Network, The Transistor andPortable Electronics. All about the history of tran-sistors and integrated circuits.

• Transistorized. Historical and technical informationfrom the Public Broadcasting Service

• This Month in Physics History: November 17 to De-cember 23, 1947: Invention of the First Transistor.From the American Physical Society

• 50 Years of the Transistor. From Science Friday, De-cember 12, 1997

Pinouts

• Common transistor pinouts

Datasheets

• Charts showing many characteristics and links tomost datasheets for 2N, 2SA, 2SB. 2SC, 2SD, 2SH-K, and other numbers.

• Discrete Databook (Historical 1978), NationalSemiconductor (now Texas Instruments)

• Discrete Databook (Historical 1982), SGS (nowSTMicroelectronics)

• Small-Signal Transistor Databook (Historical1984), Motorola

• Discrete Databook (Historical 1985), Fairchild

13

13 Text and image sources, contributors, and licenses

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14 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

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