Транзистор: Электр сигнал күшейткіш және қосқыш құрылғысының тарихы

Solid state electrically operated switch also used as an amplifier

A transistor is a semiconductor device used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic 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. Some transistors are packaged individually, but many more in miniature form are found embedded in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions. Physicist Julius Edgar Lilienfeld proposed the concept of a field effect transistor (FET) in 1926, but it was not possible to construct a working device at that time. The first working device was a point contact transistor invented in 1947 by physicists John Bardeen, Walter Brattain, and William Shockley at Bell Labs; the three shared the 1956 Nobel Prize in Physics for their achievement. The most widely used type of transistor is the metal–oxide–semiconductor field effect transistor (MOSFET), invented by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959. Physicist Julius Edgar Lilienfeld filed a patent for a field effect transistor (FET) in Canada in 1925, intended as a solid state replacement for the triode. He filed identical patents in the United States in 1926 and 1928. However, he 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, inventor Oskar Heil patented a similar device in Europe.

The basic principle of the field effect transistor (FET) was first proposed by physicist Julius Edgar Lilienfeld when he filed a patent for a device similar to MESFET in 1926, and for an insulated gate field effect transistor in 1928. The FET concept was later also theorized by engineer Oskar Heil in the 1930s and by William Shockley in the 1940s. In 1945 JFET was patented by Heinrich Welker. Following Shockley's theoretical treatment on JFET in 1952, a working practical JFET was made in 1953 by George C. Dacey and Ian M. Ross. In 1948, Bardeen patented the progenitor of MOSFET, an insulated gate FET (IGFET) with an inversion layer. Bardeen's patent, and the concept of an inversion layer, forms the basis of CMOS technology today.

In the early years of the semiconductor industry, companies focused on the junction transistor, a relatively bulky device that was difficult to mass produce, limiting it to several specialized applications. Field effect transistors (FETs) were theorized as potential alternatives, but researchers could not get them to work properly, largely due to the surface state barrier that prevented the external electric field from penetrating the material. In 1957, Bell Labs engineer Mohamed Atalla proposed a new method of semiconductor device fabrication: coating a silicon wafer with an insulating layer of silicon oxide so electricity could overcome the surface state and reliably penetrate to the semiconducting silicon below. The process, known as surface passivation, became critical to the semiconductor industry, as it enabled the mass production of silicon integrated circuits. Building on the method, he developed the metal–oxide–semiconductor (MOS) process, the first transistor that could be miniaturized and mass produced for a wide range of uses. With its high scalability, much lower power consumption, and higher density than bipolar junction transistors, the MOSFET made it possible to build high density integrated circuits, allowing the integration of more than 10,000 transistors in a single IC. CMOS (complementary MOS) was invented by Chih Tang Sah and Frank Wanlass at Fairchild Semiconductor in 1963. The first report of a floating gate MOSFET was made by Dawon Kahng and Simon Sze in 1967. A double gate MOSFET was first demonstrated in 1984 by Electrotechnical Laboratory researchers Toshihiro Sekigawa and Yutaka Hayashi. FinFET (fin field effect transistor), a type of 3D non planar multi gate MOSFET, originated from the research of Digh Hisamoto and his team at Hitachi Central Research Laboratory in 1989.

Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions. Other Milestones include the inventions of the junction transistor in 1948 and the MOSFET in 1959. The MOSFET is by far the most widely used transistor, in applications ranging from computers and electronics It has been considered the most important transistor, possibly the most important invention in electronics, and the device that enabled modern electronics. It has been the basis of modern digital electronics since the late 20th century, paving the way for the digital age. The US Patent and Trademark Office calls it a "groundbreaking invention that transformed life and culture around the world". Although several companies each produce over a billion individually packaged (known as discrete) MOS transistors every year, the vast majority are produced in integrated circuits (also known as ICs, 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 20 transistors, whereas an advanced microprocessor, as of 2022, may contain as many as 57 billion MOSFETs. Transistors are often organized into logic gates in microprocessors to perform computation. The transistor's low cost, flexibility and reliability have made it ubiquitous. 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.

The common emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor whose current amplification combined with the properties of the circuit means that small swings in Vin produce large changes in Vout.

Convenient mnemonic to remember the type of transistor (represented by an electrical symbol) involves the direction of the arrow. For the BJT, on an n p n transistor symbol, the arrow will "Not Point iN". On a p n p transistor symbol, the arrow "Points iN Proudly". However, this does not apply to MOSFET based transistor symbols as the arrow is typically reversed (i. e. the arrow for the n p n points inside).

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 (VGS) is increased, the drain–source current (IDS) increases exponentially for VGS below threshold, and then at a roughly quadratic rate: (IDS ∝ (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. 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 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 drains. 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. 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 (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, while most IGFETs are enhancement mode types.

Three major identification standards are used for designating transistor devices. In each, the alphanumeric prefix provides clues to the type of the device.

Manufacturers of devices may have their 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). Military part numbers sometimes are assigned their 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 low power JFET, the other the higher powered MOSFET 2SJ176). As older "through hole" transistors are given surface mount packaged counterparts, they tend to be assigned many different part numbers because manufacturers have their 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.

+ Semiconductor material characteristics Semiconductor material Junction forward voltage @ 25 °C, V Electron mobility @ 25 °C, m2/(V·s) Hole mobility @ 25 °C, m2/(V·s) Max. (Maximum) junction temp. (temperature), °C Ge0.270.390.1970 to 100 Si0.710.14 0.05150 to 200 GaAs1.030.850.05150 to 200 Al–Si junction0.3——150 to 200

The first BJTs were made from germanium (Ge). Silicon (Si) types currently predominate but certain advanced microwave and high performance versions now employ the compound semiconductor material gallium arsenide (GaAs) and the semiconductor alloy silicon germanium (SiGe). Single element semiconductor material (Ge and Si) is described as elemental. Rough parameters for the most common semiconductor materials used to make transistors are given in the adjacent table. These parameters will vary with an increase in temperature, electric field, impurity level, strain, and sundry other factors. The junction forward voltage is the voltage applied to the emitter base junction of a BJT 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 an 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. The density of mobile carriers in the channel of a MOSFET is a function of the electric field forming the channel and of various other phenomena such as the impurity level in the channel. Some impurities, called dopants, are introduced deliberately in making a MOSFET, to control the MOSFET electrical behavior. The electron mobility and hole mobility columns show the average speed that electrons and holes diffuse through the semiconductor material with an electric field of 1 volt per meter applied across the material. In general, the higher the electron mobility the faster the transistor can operate. The table indicates that Ge is a better material than Si in this respect. However, Ge has four major shortcomings compared to silicon and gallium arsenide:
Its maximum temperature is limited. It has relatively high leakage current. It cannot withstand high voltages. It is less suitable for fabricating integrated circuits. Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolar n–p–n transistor tends to be swifter than an equivalent p–n–p transistor. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high frequency applications. A relatively recent FET development, the high electron mobility transistor (HEMT), has a 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 aluminum gallium nitride (AlGaN/GaN HEMTs) provide still higher electron mobility and are being developed for various applications. Maximum junction temperature values represent a cross section taken from various manufacturers' datasheets. 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 can be individually packaged transistors or unpackaged transistor chips. 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. 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 ratings. Transistor packages are made of glass, metal, ceramic, or plastic. The package often dictates the power rating and frequency characteristics. Power transistors have larger packages that can be clamped to heat sinks for enhanced cooling. Additionally, most power transistors have the collector or drain physically connected to the metal enclosure. At the other extreme, some surface mount microwave transistors are as small as grains of sand. Often a given transistor type is available in several packages. Transistor packages are mainly standardized, but the assignment of a transistor's functions to the terminals is not: other transistor types can assign other functions to the package's terminals. Even for the same transistor type the terminal assignment can vary (normally indicated by a suffix letter to the part number, q. e. BC212L and BC212K). 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. Unpackaged transistor chips (die) may be assembled into hybrid devices. The IBM SLT module of the 1960s is one example of such a hybrid circuit module using glass passivated transistor (and diode) die. Other packaging techniques for discrete transistors as chips include direct chip attach (DCA) and chip on board (COB). Flexible transistors are useful in some kinds of flexible displays and other flexible electronics.