A transistor (triode, by the number of terminals) is a semiconductor radio component that typically has three electrical terminals for operation and control. The primary property of a transistor is controlling current in an electrical circuit under the influence of an external signal.
A transistor is used for generation, amplification, and conversion (waveform shaping) of electrical signals, as well as for switching (operating in a keying mode). In modern electronics, the transistor is the foundation of circuit design in the vast majority of devices (in amplifiers, oscillators, comparator circuits and other similar solutions) and integrated circuits. Today, the number of transistors in electronic chips (microchips, integrated circuits) is measured in billions.
Structurally, a transistor consists of three electrodes: base, emitter, and collector. The emitter and collector are the power (working) terminals, and the base provides control. On circuit diagrams, a transistor is depicted as three leads enclosed in a circle. The arrow indicates the direction of current in the emitter.
Semiconductor materials predominantly used in transistors include silicon, gallium arsenide, and germanium. There are also transistors based on carbon nanotubes, transparent variants for LCD displays, and polymer transistors (the most promising).
Types of transistors
Transistors differ by electrical structure and operating principle and are divided into two classes — bipolar and field-effect. In a bipolar transistor, semiconductors with both conductivity types are used. A bipolar transistor operates through the interaction of two p-n junctions and is controlled by changing the current through the base–emitter junction.
In a field-effect transistor
a semiconductor of a single conductivity type forms a thin channel influenced by the electric field of a gate isolated from the channel. Control is performed by changing the voltage between the gate and the source. Unlike a bipolar device, a field-effect transistor is voltage-controlled rather than current-controlled.
In analog electronics, bipolar transistors are predominant, while in digital electronics, within integrated circuits (logic, memory, processors, computers, digital communications, etc.), field-effect transistors predominate.
Transistors also differ by electrical parameters:
- by power rating (low-power, power devices)
- by signal frequency (low-frequency, high-frequency (VHF/UHF))
Related articles:
Field-effect transistor — overview
,
Comparator — definition and purpose,
Potentiometer — operating principle,
Trigger (flip-flop) — basics,
Thermocouple — fundamentals,
Diode — introduction,
Solid State Relay — application,
Imported analogs of domestic transistors
Transistor 2T818A, 2T818B, 2T818V, 2T818A2, 2T818B2, 2T818V2, KT818A, KT818B, KT818V, KT818G, KT818AM, KT818BM, KT818VM, KT818GM, KT818A1, KT818B1, KT818V1, K7818G1 specifications