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A transistor is a semiconductor device that exhibits all the properties of a switch, allowing or blocking the flow of electrons. It has three terminals, one for input, one for output and one for controlling switching. It is the fundamental building block of modern electronic devices and is commonly found in circuit boards as discrete parts or embedded into integrated circuits.
The transistor is composed of a semiconductive material, usually silicon, and at least three terminals for connecting to the external circuit. It was invented in 1947 by William Shockley, Walter Brattain and John Bardeen, who were jointly awarded the Nobel Prize in Physics for catapulting technological development. Their achievement is responsible for such modern appliances as wide screen TVs, smartphones, tablets and other electronic computing devices.
The most basic function of a transistor is as an electronic switch, which allows electrons to flow from its collector side out through the emitter side. The base or middle of the transistor acts as the real switch control electrode through which electron stimulation rapidly changes the material from an insulator to conductive state, thereby allowing the flow of electricity.
Transistors are created through a chemical process known as doping, where the semiconductive material either gains an extra negative charge (N-type) or extra positive charge (P-type). There are two configurations for this, either PNP or NPN with the middle material acting as the base or flow control.
A very small change in the current or voltage in the middle base layer results in a large amount of electricity flowing through the whole component. In this aspect, it can be used as an amplifier.