A TRANSISTOR is a semiconductor device used to amplify or switch electronic signals and electrical power . It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits .
The transistor is the fundamental building block of modern electronic devices , and is ubiquitous in modern electronic systems. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to actually construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen , Walter Brattain , and William Shockley . The transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios , calculators , and computers , among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, and Shockley shared the 1956 Nobel Prize in Physics for their achievement.
* 1 History * 2 Importance
* 3 Simplified operation
* 4 Comparison with vacuum tubes
* 4.1 Advantages * 4.2 Limitations
* 5 Types
* 6 Part numbering standards/specifications
* 6.1 Japanese Industrial Standard (JIS) * 6.2 European Electronic Component Manufacturers Association (EECA)
* 6.3 Joint
* 7 Construction
* 7.2 Packaging
* 7.2.1 Flexible transistors
* 8 See also * 9 Directory of external websites with datasheets * 10 References * 11 Further reading * 12 External links
Main article: History of the transistor A replica of the first working transistor.
The thermionic triode , a vacuum tube invented in 1907, enabled
amplified radio technology and long-distance telephony . The triode,
however, was a fragile device that consumed a substantial amount of
power. In 1909 physicist
William Eccles discovered the crystal diode
oscillator. German 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 replacement for the triode. Lilienfeld
also filed identical patents in the United States in 1926 and 1928.
However, Lilienfeld did not publish any research articles about his
devices nor did his patents cite any specific examples of a working
prototype. Because the production of high-quality semiconductor
materials was still decades away, Lilienfeld's solid-state amplifier
ideas would not have found practical use in the 1920s and 1930s, even
if such a device had been built. In 1934, German inventor Oskar Heil
patented a similar device in Europe.
John Bardeen , William
Walter Brattain at
From November 17, 1947 to December 23, 1947, John Bardeen and Walter Brattain at AT"> Herbert F. Mataré (1950)
In 1948, the point-contact transistor was independently invented by
Herbert Mataré and
Heinrich Welker while working at
the _Compagnie des Freins et Signaux_, a Westinghouse subsidiary
The first bipolar junction transistors were invented by Bell Labs'
William Shockley, which applied for patent(2,569,347) on June 26,
1948. On April 12, 1950,
The first high-frequency transistor was the surface-barrier germanium
transistor developed by
Philco in 1953, capable of operating up to 60
MHz. 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.
The first "prototype" pocket transistor radio was shown by INTERMETALL (a company founded by Herbert Mataré in 1952) at the _Internationale Funkausstellung Düsseldorf_ between August 29, 1953 and September 9, 1953.
The first "production" all-transistor radio was the Regency TR-1 , released in October 1954. Produced as a joint venture between the Regency Division of Industrial Development Engineering Associates, I.D.E.A. and Texas Instruments of Dallas Texas, the TR-1 was manufactured in Indianapolis, Indiana. It was a near pocket-sized radio featuring 4 transistors and one germanium diode. The industrial design was outsourced to the Chicago firm of industrial design firm of Painter, Teague and Petertil. It was initially released in one of four different colours: black, bone white, red, and gray. Other colours were to shortly follow.
The first working silicon transistor was developed at
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. Its importance in today's society rests on its ability to be 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 IEEE Milestone in 2009.
Although several companies each produce over a billion individually packaged (known as _discrete _) transistors every year, the vast majority of transistors are now produced in integrated circuits (often shortened to _IC_, _microchips_ or simply _chips_), along with diodes , resistors , capacitors and other electronic components , 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 (MOSFETs ). "About 60 million transistors were built in 2002… for man, woman, and child on Earth."
The transistor's low cost, flexibility, and reliability have made it a ubiquitous device. Transistorized mechatronic circuits have replaced electromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical system to control that same function.
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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 . It can produce a stronger output signal, a voltage or current, which is proportional to a weaker 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 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_BE.
TRANSISTOR AS A SWITCH
Transistors are commonly used in digital circuits as electronic switches which can be either in an "on" or "off" state, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates . Important parameters for this application include the current switched, the voltage handled, and the switching speed, characterised by the rise and fall times .
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_.
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 a switching circuit, the idea is to simulate, as near as possible, the ideal switch having the properties of open circuit when off, short circuit when on, and an instantaneous transition between the two states. Parameters are chosen such that the "off" output is limited to leakage currents too small to affect connected circuitry; the resistance of the transistor in the "on" state is too small to affect circuitry; and the transition between the two states is fast enough not to have a detrimental effect.
TRANSISTOR AS AN AMPLIFIER
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_in) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit means that small swings in _V_in produce large changes in _V_out.
Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.
From mobile phones to televisions , vast numbers of products include amplifiers for sound reproduction , radio transmission , and signal processing . The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.
Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.
COMPARISON WITH VACUUM TUBES
Before transistors were developed, vacuum (electron) tubes (or in the UK "thermionic valves" or just "valves") were the main active components in electronic equipment.
The key advantages that have allowed transistors to replace vacuum tubes in most applications are
* no cathode heater (which produces the characteristic orange glow of tubes), reducing power consumption, eliminating delay as tube heaters warm up, and immune from cathode poisoning and depletion; * very small size and weight, reducing equipment size; * large numbers of extremely small transistors can be manufactured as a single integrated circuit ; * low operating voltages compatible with batteries of only a few cells; * circuits with greater energy efficiency are usually possible. For low-power applications (e.g., voltage amplification) in particular, energy consumption can be very much less than for tubes; * inherent reliability and very long life; tubes always degrade and fail over time. Some transistorized devices have been in service for more than 50 years ; * complementary devices available, providing design flexibility including complementary-symmetry circuits, not possible with vacuum tubes; * very low sensitivity to mechanical shock and vibration, providing physical ruggedness and virtually eliminating shock-induced spurious signals (e.g., microphonics in audio applications); * not susceptible to breakage of a glass envelope, leakage, outgassing, and other physical damage.
Transistors have the following limitations:
* silicon transistors can age and fail; * high-power, high-frequency operation, such as that used in over-the-air television broadcasting , is better achieved in vacuum tubes due to improved electron mobility in a vacuum; * solid-state devices are susceptible to damage from very brief electrical and thermal events, including electrostatic discharge in handling; vacuum tubes are electrically much more rugged; * sensitivity to radiation and cosmic rays (special radiation-hardened chips are used for spacecraft devices); * vacuum tubes in audio applications create significant lower-harmonic distortion, the so-called tube sound , which some people prefer.
Transistors are categorized by
* semiconductor material : the metalloids germanium (first used in
1947) and silicon (first used in 1954)—in amorphous ,
polycrystalline and monocrystalline form—, the compounds gallium
arsenide (1966) and silicon carbide (1997), the alloy
silicon-germanium (1989), the allotrope of carbon graphene (research
ongoing since 2004), etc. (see
Hence, a particular transistor may be described as _silicon, surface-mount, BJT, n–p–n, low-power, high-frequency switch_.
A popular way to remember which symbol represents which type of transistor is to look at the arrow and how it is arranged. Within an NPN transistor symbol, the arrow will Not Point iN. Conversely, within the PNP symbol you see that the arrow Points iN Proudly.
BIPOLAR JUNCTION TRANSISTOR (BJT)
Main article: Bipolar junction transistor
Bipolar transistors are so named because they conduct by using both majority and minority carriers . The bipolar junction transistor, the first type of transistor to be mass-produced, is a combination of two junction diodes, and is formed of either a thin layer of p-type semiconductor sandwiched between two n-type semiconductors (an n–p–n transistor), or a thin layer of n-type semiconductor sandwiched between two p-type semiconductors (a p–n–p transistor). This construction produces two p–n junctions : a base–emitter junction and a base–collector junction, separated by a thin region of semiconductor known as the base region (two junction diodes wired together without sharing an intervening semiconducting region will not make a transistor).
BJTs have three terminals, corresponding to the three layers of semiconductor—an _emitter_, a _base_, and a _collector_. They are useful in amplifiers because the currents at the emitter and collector are controllable by a relatively small base current. In an n–p–n transistor operating in the active region, the emitter–base junction is forward biased (electrons and holes recombine at the junction), and electrons are injected into the base region. Because the base is narrow, most of these electrons will diffuse into the reverse-biased (electrons and holes are formed at, and move away from the junction) base–collector junction and be swept into the collector; perhaps one-hundredth of the electrons will recombine in the base, which is the dominant mechanism in the base current. By controlling the number of electrons that can leave the base, the number of electrons entering the collector can be controlled. Collector current is approximately β (common-emitter current gain) times the base current. It is typically greater than 100 for small-signal transistors but can be smaller in transistors designed for high-power applications.
Unlike the field-effect transistor (see below), the
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 phototransistors .
FIELD-EFFECT TRANSISTOR (FET)
Field-effect transistor ,
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_GS) is increased, the drain–source current (_I_DS) increases exponentially for _VGS_ below threshold, and then at a roughly quadratic rate (_I_DS ∝ (_V_GS − _V_T)2) (where _V_T is the threshold voltage at which drain current begins) in the "space-charge-limited " region above threshold. A quadratic behavior is not observed in modern devices, for example, at the 65 nm technology node.
For low noise at narrow bandwidth the higher input resistance of the FET is advantageous.
FETs are divided into two families: _junction FET_ (
JFET ) and
_insulated gate FET_ (IGFET). The IG
FET is more commonly known as a
_metal–oxide–semiconductor FET_ (
Metal–semiconductor FETs (MESFETs ) are JFETs in which the reverse biased p–n junction is replaced by a metal–semiconductor junction . These, and the HEMTs (high-electron-mobility transistors, or HFETs), in which a two-dimensional electron gas with very high carrier mobility is used for charge transport, are especially suitable for use at very high frequencies (microwave frequencies; several GHz).
FETs are further divided into _depletion-mode_ and _enhancement-mode_ types, depending on whether the channel is turned on or off with zero gate-to-source voltage. For enhancement mode, the channel is off at zero bias, and a gate potential can "enhance" the conduction. For the depletion mode, the channel is on at zero bias, and a gate potential (of the opposite polarity) can "deplete" the channel, reducing conduction. For either mode, a more positive gate voltage corresponds to a higher current for n-channel devices and a lower current for p-channel devices. Nearly all JFETs are depletion-mode because the diode junctions would forward bias and conduct if they were enhancement-mode devices; 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
OTHER TRANSISTOR TYPES
* Bipolar junction transistor (BJT):
* heterojunction bipolar transistor , up to several hundred GHz, common in modern ultrafast and RF circuits; * Schottky transistor ; * avalanche transistor : * Darlington transistors are two BJTs connected together to provide a high current gain equal to the product of the current gains of the two transistors; * insulated-gate bipolar transistors (IGBTs) use a medium-power IGFET, similarly connected to a power BJT, to give a high input impedance. Power diodes are often connected between certain terminals depending on specific use. IGBTs are particularly suitable for heavy-duty industrial applications. The ASEA Brown Boveri (ABB) 5SNA2400E170100_ illustrates just how far power semiconductor technology has advanced. Intended for three-phase power supplies, this device houses three n–p–n IGBTs in a case measuring 38 by 140 by 190 mm and weighing 1.5 kg. Each IGBT is rated at 1,700 volts and can handle 2,400 amperes; * phototransistor ; * multiple-emitter transistor , used in transistor–transistor logic and integrated current mirrors; * multiple-base transistor , used to amplify very-low-level signals in noisy environments such as the pickup of a record player or radio front ends . Effectively, it is a very large number of transistors in parallel where, at the output, the signal is added constructively, but random noise is added only stochastically .
* Field-effect transistor (FET):
* carbon nanotube field-effect transistor (CNFET), where the channel material is replaced by a carbon nanotube; * junction gate field-effect transistor (JFET), where the gate is insulated by a reverse-biased p–n junction;
* metal–semiconductor field-effect transistor (MESFET), similar to JFET with a Schottky junction instead of a p–n junction;
* high-electron-mobility transistor (HEMT);
* metal–oxide–semiconductor field-effect transistor (MOSFET), where the gate is insulated by a shallow layer of insulator; * inverted-T field-effect transistor (ITFET); * fin field-effect transistor (FinFET), source/drain region shapes fins on the silicon surface; * fast-reverse epitaxial diode field-effect transistor (FREDFET); * 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;
* ion-sensitive field-effect transistor (IFSET), to measure ion concentrations in solution, * electrolyte–oxide–semiconductor field-effect transistor (EOSFET), neurochip , * deoxyribonucleic acid field-effect transistor (DNAFET).
Tunnel field-effect transistor , where it switches by modulating
quantum tunnelling through a barrier.
Diffusion transistor , formed by diffusing dopants into
semiconductor substrate; can be both
* Multigate devices :
* tetrode transistor ; * pentode transistor ; * trigate transistor (prototype by Intel); * dual-gate field-effect transistors have a single channel with two gates in cascode ; a configuration optimized for _high-frequency amplifiers_, _mixers_, and oscillators .
* Junctionless nanowire transistor (JNT), uses a simple nanowire of silicon surrounded by an electrically isolated "wedding ring" that acts to gate the flow of electrons through the wire. * Vacuum-channel transistor , when in 2012, NASA and the National Nanofab Center in South Korea were reported to have built a prototype vacuum-channel transistor in only 150 nanometers in size, can be manufactured cheaply using standard silicon semiconductor processing, can operate at high speeds even in hostile environments, and could consume just as much power as a standard transistor. * Organic electrochemical transistor .
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)
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-C-7012 _ specification for transistor part numbers starts with "2S", e.g. 2SD965, but sometimes the "2S" prefix is not marked on the package – a 2SD965 might only be marked "D965"; a 2SC1815 might be listed by a supplier as simply "C1815". This series sometimes has suffixes (such as "R", "O", "BL", standing for "red", "orange", "blue", etc.) to denote variants, such as tighter _h_FE (gain) groupings.
EUROPEAN ELECTRONIC COMPONENT MANUFACTURERS ASSOCIATION (EECA)
AC Germanium small-signal AF transistor AC126 NTE102A Datasheet
AD Germanium AF power transistor AD133 NTE179 Datasheet
AF Germanium small-signal RF transistor AF117 NTE160 Datasheet
AL Germanium RF power transistor ALZ10 NTE100 Datasheet
AS Germanium switching transistor ASY28 NTE101 Datasheet
AU Germanium power switching transistor AU103 NTE127 Datasheet
BC Silicon, small-signal transistor ("general purpose") BC548 2N3904 Datasheet
BD Silicon, power transistor BD139 NTE375 Datasheet
BL Silicon, high frequency, high power (for transmitters) BLW60 NTE325 Datasheet
BU Silicon, high voltage (for CRT horizontal deflection circuits) BU2520A NTE2354 Datasheet
JOINT ELECTRON DEVICE ENGINEERING COUNCIL (JEDEC)
The JEDEC _EIA370_ transistor device numbers usually start with "2N", indicating a three-terminal device (dual-gate field-effect transistors 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.
Manufacturers of devices may have their own proprietary numbering
system, for example
CK722 . Since devices are second-sourced , a
manufacturer's prefix (like "MPF" in MPF102, which originally would
Military part numbers sometimes are assigned their own codes, such as the British Military CV Naming System .
Manufacturers buying large numbers of similar parts may have them supplied with "house numbers", identifying a particular purchasing specification and not necessarily a device with a standardized registered number. For example, an HP part 1854,0053 is a (JEDEC) 2N2218 transistor which is also assigned the CV number: CV7763
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
JFET , the other the higher-powered
As older "through-hole" transistors are given 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.
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).
Rough parameters for the most common semiconductor materials used to make transistors are given in the adjacent table; 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
The density of mobile carriers in the channel of a
The _electron mobility _ and _hole mobility _ columns show the average speed that electrons and holes diffuse through the semiconductor material with an electric field of 1 volt per meter applied across the material. In general, the higher the electron mobility the faster the transistor can operate. The table indicates that Ge is a better material than Si in this respect. However, Ge has four major shortcomings compared to silicon and gallium arsenide:
* Its maximum temperature is limited; * it has relatively high leakage current ; * it cannot withstand high voltages; * it is less suitable for fabricating integrated circuits.
Because the electron mobility is higher than the hole mobility for
all semiconductor materials, a given bipolar n–p–n transistor
tends to be swifter than an equivalent p–n–p transistor . GaAs has
the highest electron mobility of the three semiconductors. It is for
this reason that GaAs is used in high-frequency applications. A
FET development, the _high-electron-mobility
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 _ reverse Schottky diode formed between the source and drain as part of the fabrication process. This diode can be a nuisance, but sometimes it is used in the circuit.
DISCRETE TRANSISTORS are individually packaged transistors. Transistors come in many different semiconductor packages (see image). The two main categories are _through-hole _ (or _leaded_), and _surface-mount_, also known as _surface-mount device_ (SMD ). The _ball grid array_ (BGA ) is the latest surface-mount package (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.
Often a given transistor type is available in several packages.
Nowadays most transistors come in a wide range of SMT packages, in comparison the list of available through-hole packages is relatively small, here is a short list of the most common through-hole transistors packages in alphabetical order: ATV, E-line, MRT, HRT, SC-43, SC-72, TO-3, TO-18, TO-39, TO-92, TO-126, TO220, TO247, TO251, TO262, ZTX851
Researchers have made several kinds of flexible transistors, including organic field-effect transistors . Flexible transistors are useful in some kinds of flexible displays and other flexible electronics .
DIRECTORY OF EXTERNAL WEBSITES WITH DATASHEETS
* 2N3904/2N3906, BC182/BC212 and BC546/BC556: Ubiquitous, BJT,
general-purpose, low-power, complementary pairs. They have plastic
cases and cost roughly ten cents U.S. in small quantities, making them
popular with hobbyists.
AF107 : Germanium, 0.5 watt, 250 MHz p–n–p BJT.
* BFP183: Low-power, 8 GHz microwave n–p–n BJT.
* LM394: "supermatch pair", with two n–p–n BJTs on a single
* 2N2219A/2N2905A: BJT, general purpose, medium power, complementary
pair. With metal cases they are rated at about one watt.
* 2N3055/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 MHz, 15 A, 60 V, 115 W BJTs are used in
audio-power amplifiers, power supplies, and control.
* 2SC3281/2SA1302: Made by
* ^ "1926 – Field Effect
* Amos SW & James MR (1999). _Principles of