The transistor is the electronic Electronics component active fundamental in used mainly like ordered Interrupteur and for amplification, but also to stabilize a tension, to modulate a Signal as well as many other uses.

The term transistor comes from the English transconductance resistor (variable resistor of transconductance). He was voted by a management committee of 26 people of the Bell Labs on May 28th 1948 (memo 48-130-10), among the names suggested following: semiconductor three-electrode, three-electrode surface states, three-electrode hook, solid three-electrode, iotatron, transistor. For trade names, one needed a short, unambiguous name with the technology of the electron tubes. Transistor was selected. It indicates a device Semi-conducteur with three active electrodes which allows control thanks to a electrode of entry (bases for the bipolar ones and roasts for the FET) of a current or a tension on one of the output electrodes (collector for the bipolar ones and drain for the FET).

By Métonymie, the transistor term also indicates the receiving radio operator equipped with transistors.

History

The transistor effect was discovered in 1934 by the American John Bardeen, William Shockley and Walter Brattain, researchers of the company Bell Téléphone. They received the Nobel Prize of physics in 1956.

The transistor was regarded as an enormous progress vis-a-vis the electron Tube: much smaller, light, it is more robust, it functions with weak tensions, it can thus be supplied with piles and it functions instantaneously once energized, contrary to the electron tubes which asked for ten of seconds of heating, generated an important consumption and required a source of high tension (several hundreds of volts)

It was quickly assembled, with other components, within integrated circuits, which enabled him to conquer even more ground on the other forms of active electronics.

The transistor constituted a determining invention without which electronics and the Informatique would not have their current forms (2007); it allowed the company electronic Information to develop.

Classification

Bipolar transistor

See also: bipolar Transistor

Field-effect transistor

See also: Field-effect transistor

Among the field-effect transistors (or FET , for Field Effect Transistor ), one can distinguish the following families:

• Transistors MOSFET: they use the properties of the structures Métal/Oxyde/Semiconducteur;
• Transistors JFET: they use the properties of junctions PN; their implementation (diagrams, calculation of the elements of the circuit and the characteristics of the assemblies) is described in the article Transistor JFET.

Transistor with double-base diode

• the transistor known as double-base diode , which is not used almost any more, but was used to create Oscillateur S with relieving.

Hybrid technology

• IGBT, is an hybrid of bipolar and MOSFET, only used in electronic of power.

Applications

The two principal types of transistors make it possible to meet the needs for electronics Analogique, Numérique, of the electronic of power and High voltage.

* technology bipolar is rather used into analogical and electronic of power.

* technologies FET and CMOS are mainly used in numerical electronics (realization of logical operations). They can be used to make analogical blocks in digital circuits (voltage regulator for example). They are also used to make power controls (engines) and electronics high voltage (automobile). Their characteristics are connected more with those of the electron tubes. They offer a better linearity within the framework of Hi-Fi amplifiers, therefore less distortion.

* a mixture of two technologies is used in IGBT

Constitution

The Substrat S used go from the Germanium (series AC, now obsolete), while passing by the Silicium, the Gallium arsenide, the Silicon-germanium and more recently the Carbure of silicon, the Nitrure of gallium, the indium antimonide.

For the large majority of the applications, one uses silicon whereas the more exotic materials such as gallium arsenide and gallium nitride are rather used to produce the transistors ultra high frequency and microwave.

• a bipolar transistor is composed of two identically doped parts of semiconductor substrate (P or NR) separated by a thin section from semiconductor doped conversely; there are thus two types: N-P-N and P-N-P;
• the transistor with field effect classically is composed of a bar of semiconductor doped NR or P, and surrounded in its medium of a ring of semiconductor doped conversely (P or NR). One speaks about FET with channel NR or P following the doping of the bar;
• the transistor MOS is composed of a bar of semiconductor P or NR on which one makes grow by epitaxy a thin layer of insulator (Silice for example), which is surmounted by a metal electrode.

Diagrammatic description

Three connections are called:

For the bipolar transistor, the arrow identifies the transmitter; it in the case of points towards outside a NPN, the interior in the case of a PNP. The electrode connected to the straight line appears the base and the other electrode appears the collector.

In the case of the field effect , the arrow disappears, because the device is symmetrical (drain and source are exchangeable). The oblique features are usually replaced by right features.

For the transistor MOS , the grid is detached from the other electrodes, to indicate the insulation due to the presence of oxide.

Actually, there exists the fourth connection for the field-effect transistors, the Substrat (sometimes called bulk ), which is usually connected to the source (it is connection between S and the two features vertical on the diagram).

Principle of operation

The transistors bipolar MOS and function in way very different:

• the bipolar transistor is a Amplificateur of current, one injects a current in space bases/transmitting in order to create a current multiplied by the profit of the transistor between the transmitter and the collector.
• the bipolar transistors N.P.N. (negative-positive-negative) let circulate a current of the base (+) towards the transmitter (-) are faster and have the best held in tension than transistors P.N.P. bases (-) transmitting (+), but can be produced with complementary characteristics by the manufacturers for the applications requiring it.
• the field-effect transistor . Its control unit is the grid (spoils in English). This one needs only a tension (or a potential) between the grid and the source to control the current between the source and the drain. The running of grid is null (or negligible) in static mode, since the grid behaves with respect to the control circuit like a condenser of low capacity.

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