Transistor

context: A transistor is a semiconductor device used to amplify or switch 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 current applied to one pair of the transistor's terminals changes 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.
qas: answers: text: to amplify or switch electronic signals and electrical power
question: What is the use of a transistor?

answers: text: semiconductor material
question: What is a transistor made of?

answers: text: the controlled (output) power can be higher than the controlling (input) power
question: Why does a transistor increase a signal?

answers: text: three
question: What is the minimum amount of external connection terminals to call an item a transistor?

answers: text: embedded in integrated circuits
question: Where are most transistors found?

context: The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. First conceived by Julius Lilienfeld in 1926 and practically implemented 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.
qas: answers: text: 1926
question: When was the first transistor created?

answers: text: Julius Lilienfeld
question: Who invented the first transistor?

answers: text: 1947
question: When was the first transistor implemented for practical use?

answers: text: 1956
question: When did the implementers receive a Nobel Prize for making the transistor?

answers: text: list of IEEE milestones in electronics
question: What list is the transistor on?

context: 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 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 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.
qas: answers: text: 1907
question: When was the thermionic triode invented?

answers: text: amplified radio technology and long-distance telephony
question: What was the purpose of the thermionic triode?

answers: text: Physicist Julius Edgar Lilienfeld
question: Who filed a patent for the field-effect transistor?

answers: text: Canada
question: Where did Lilienfeld file his patent?

answers: text: 1925
question: What year did Lilienfeld file his patent?

context: From November 17, 1947 to December 23, 1947, John Bardeen and Walter Brattain at 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. Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term transistor was coined by John R. Pierce as a contraction of the term transresistance. According to Lillian Hoddeson and Vicki Daitch, 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. 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."
qas: answers: text: November 17, 1947 to December 23, 1947
question: At what time did Bardeen and Brattain experiment on increasing signal output?

answers: text: germanium
question: What were gold contacts attached to to increase signal output?

answers: text: William Shockley
question: Who was the Solid State Physics Group Leader?

answers: text: John R. Pierce
question: Who came up with the term transistor?

answers: text: a contraction of the term transresistance
question: Why was the term transistor used?

context: 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 subsidiary located in Paris. Mataré had previous experience in developing 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" in 1947. By June 1948, witnessing currents flowing through point-contacts, Mataré produced consistent results using samples of germanium produced by Welker, similar to what Bardeen and Brattain had accomplished earlier in December 1947. Realizing that Bell Labs' scientists had already invented the transistor before them, the company rushed to get its "transistron" into production for amplified use in France's telephone network.
qas: answers: text: 1948
question: In what year was the point-contact transistor invented?

answers: text: Compagnie des Freins et Signaux
question: Where were Matare and Welker working when inventing the point-contact transistor?

answers: text: Herbert Mataré and Heinrich Welker
question: Who invented the point-contact transistor?

answers: text: transistron
question: What was the name of Matare and Welker's transistor?

answers: text: amplified use in France's telephone network
question: What was the transistron used for?

context: 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 [each] man, woman, and child on Earth."
qas: answers: text: up to about twenty transistors
question: How many transistors make up a logic gate?

answers: text: as many as 3 billion transistors
question: How many transistors make up a microprocessor?

answers: text: 60 million transistors were built in 2002… for [each] man, woman, and child
question: How many transistors were made in 2002?

answers: text: over a billion
question: How many individually packaged transistors are produced each year?

answers: text: IC, microchips or simply chips
question: What are some abbreviations for integrated circuits?

context: 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.
qas: answers: text: gain
question: Why is a transistor so useful?

answers: text: it can act as an amplifier
question: What is gain?

answers: text: turn current on or off in a circuit
question: What is an additional use of the transistor?

answers: text: other circuit elements
question: What determines the amount of current in an electrically controlled switch?

context: 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.
qas: answers: text: two
question: How many types of transistors are there?

answers: text: A small current at the base terminal
question: What controls the large current between the collector and emitter?

answers: text: gate, source, and drain
question: What are the components of a field-effect transistor?

answers: text: a voltage at the gate
question: In a field-effect transistor, what controls the current between the source and drain?

answers: text: base, collector, and emitter
question: What are the components of a bipolar transistor?

context: 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.
qas: answers: text: reduced resistance from collector to emitter
question: Why does the collector voltage drop in grounded-emitter transistor circuits?

answers: text: the collector current would be limited only by the load resistance (light bulb) and the supply voltage
question: What would happen if the voltage difference from collector and emitter were zero?

answers: text: saturation
question: What is the term for a zero difference between collector and emitter?

answers: text: current is flowing from collector to emitter freely
question: Why is the term saturation named as such?

answers: text: on
question: What position is the switch in when saturated?

context: 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.
qas: answers: text: Providing sufficient base drive current
question: What is a major problem with using bipolar transistors as switches?

answers: text: current gain
question: What does the transistor provide?

answers: text: the type of transistor
question: What determines the current ratio in transistors?

answers: text: collector current
question: If the type of transistor is the same what determines the current ratio?

context: 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.
qas: answers: text: the "off" output is limited to leakage currents too small to affect connected circuitry
question: How are parameters chosen in a switching circuit?

answers: text: short circuit
question: What is a switching circuit trying to simulate when on?

answers: text: open circuit
question: What is a switching circuit trying to simulate when off?

answers: text: instantaneous
question: How quickly does the change from open circuit to short circuit happen?

context: 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).
qas: answers: text: they conduct by using both majority and minority carriers
question: What gives bipolar transistors their name?

answers: text: bipolar junction transistor
question: What was the first mass-produced transistor?

answers: text: two junction diodes
question: What is the bipolar junction transistor a combination of?

answers: text: n–p–n transistor
question: What is the name for a layer of p-type semiconductor set between two n-type semiconductors?

answers: text: p–n–p transistor
question: What is the name for a layer of n-type semiconductor set between two p-type semiconductors?

context: 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.
qas: answers: text: three
question: How many terminals do BJTs have?

answers: text: three
question: How many layers of semiconductor do BJTs have?

answers: text: an emitter, a base, and a collector
question: What are the layers of semiconductor in a BJT?

answers: text: β (common-emitter current gain) times the base current
question: How can one find the amount of collector current?

answers: text: greater than 100
question: What is the usual collector current for small-signal transistors?

context: 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 (VGS) is increased, the drain–source current (IDS) increases exponentially for VGS below threshold, and then at a roughly quadratic rate (IGS ∝ (VGS − VT)2) (where VT 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.
qas: answers: text: electric field that is produced when a voltage is applied between the gate and source terminals
question: What determines the conductivity in a FET?

answers: text: the voltage applied between the gate and source
question: What controls the current between the drain and source?

answers: text: a roughly quadratic rate
question: At what rate is the drain-source current increased when the gate-source current is increased?

answers: text: in modern devices
question: Where is a quadratic behavior not observed?

context: 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 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.
qas: answers: text: two
question: How many groups are FETs split into?

answers: text: the JFET gate forms a p–n diode with the channel
question: How is a JFET different from an IGFET?

answers: text: junction FET (JFET) and insulated gate FET (IGFET)
question: What are the names of the groups of FETs

answers: text: depletion mode
question: What mode do both JFET and IGFET operate in?

answers: text: a metal–oxide–semiconductor FET (MOSFET)
question: What is the common term for an IFGET?

context: 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.
qas: answers: text: depletion-mode and enhancement-mode types
question: How are FET's separated?

answers: text: at zero bias
question: At what point is a channel off in enhancement-mode?

answers: text: at zero bias
question: At what point is a channel on in depletion-mode?

answers: text: n-channel devices
question: What channel corresponds with high current?

answers: text: p-channel devices
question: What channel corresponds with low current?

context: 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.
qas: answers: text: bipolar junction transistor
question: What was the most frequently used transistor in the 1960s and 70s?

answers: text: their greater linearity and ease of manufacture
question: Why were BJTs so popular?

answers: text: transistor applications, including analog circuits, voltage regulators, amplifiers, power transmitters and motor drivers
question: What are some applications of discrete MOSFETs?

answers: text: MOSFETs
question: What were the most popular digital circuits of the time?

context: 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 hFE, such as in: BC549C) or other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A). The more common prefixes are:
qas: answers: text: European Electronic Component Manufacturers Association part numbering scheme
question: What is the Pro Electron standard?

answers: text: two letters
question: How many letters does the part numbering scheme begin with?

answers: text: the semiconductor type
question: What is the first letter in the part numbering scheme?

answers: text: the intended use
question: What is the second letter in the part numbering scheme?

answers: text: A 3-digit sequence number
question: What follows the 2 letters in the part numbering scheme?

context: 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.
qas: answers: text: 2N
question: What does the JEDEC EIA370 transistor number start with?

answers: text: a three-terminal device
question: what does the 2N is the JEDEC EIA370 mean?

answers: text: a 2, 3 or 4-digit sequential number with no significance as to device properties
question: What follows the 2N in a JEDEC EIA370?

answers: text: a newer variant
question: What does a letter at the end of a device number mean?

answers: text: a p–n–p germanium switching transistor
question: What does the number 2N1301 indicate?

context: 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 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).
qas: answers: text: a manufacturer's prefix
question: What was once an indicator of the devices creator?

answers: text: devices are second-sourced
question: What makes a manufacturer's prefix less reliable?

answers: text: PN2222A
question: What is the marking for a 2N2222A in a plastic case?

answers: text: PN108
question: What is a plastic version of a BC108?

context: The junction forward voltage is the voltage applied to the emitter–base junction of a BJT in order to make the base conduct a specified current. The current increases exponentially as the junction forward voltage is increased. The values given in the table are typical for a current of 1 mA (the same values apply to semiconductor diodes). The lower the junction forward voltage the better, as this means that less power is required to "drive" the transistor. The junction forward voltage for a given current decreases with increase in temperature. For a typical silicon junction the change is −2.1 mV/°C. In some circuits special compensating elements (sensistors) must be used to compensate for such changes.
qas: answers: text: the voltage applied to the emitter–base junction of a BJT
question: What is the junction forward voltage?

answers: text: to make the base conduct a specified current
question: What is the purpose of a junction forward voltage?

answers: text: lower
question: What is the ideal junction forward voltage?

answers: text: less power is required to "drive" the transistor
question: Why is the ideal junction forward voltage lower?

answers: text: decreases
question: When happens to the junction forward voltage when temperature is raised?

context: Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolar n–p–n transistor tends to be swifter than an equivalent p–n–p transistor. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high-frequency applications. A relatively recent FET development, the high-electron-mobility transistor (HEMT), has a heterostructure (junction between different semiconductor materials) of aluminium gallium arsenide (AlGaAs)-gallium arsenide (GaAs) which has twice the electron mobility of a GaAs-metal barrier junction. Because of their high speed and low noise, HEMTs are used in satellite receivers working at frequencies around 12 GHz. HEMTs based on gallium nitride and aluminium gallium nitride (AlGaN/GaN HEMTs) provide a still higher electron mobility and are being developed for various applications.
qas: answers: text: GaAs
question: What semiconductor has the highest electron mobility?

answers: text: a given bipolar n–p–n transistor
question: What is quicker, a bipolar n-p-n transistor or a p-n-p transistor?

answers: text: high-frequency applications
question: What is the common application of GaAs?

answers: text: high-electron-mobility transistor
question: What does HEMT stand for?

answers: text: satellite receivers
question: What are common applications of HEMT?

context: 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.
qas: answers: text: individually packaged transistors
question: What is a discrete transistor?

answers: text: through-hole (or leaded), and surface-mount
question: What are the two most common types of transistor?

answers: text: ball grid array (BGA)
question: What is the newest surface-mount transistor?

answers: text: surface-mount device (SMD)
question: What is another name for the surface-mount transistor?

answers: text: solder "balls" on the underside in place of leads
question: What is a ball grid array composed of?