In the analog world of continuously varying signals, a transistor is a device used to amplify its electrical input. In the digital world of computing, a transistor is mostly a binary switch and the fundamental building block of digital circuitry. Like a light switch on the wall, the transistor acts as a simple on/off switch, either preventing or allowing current to flow through.
Made of Semiconductor Material
The active part of the transistor is made of silicon or some other semiconductor material that can change its electrical state when pulsed. In its normal state, the material may be nonconductive or conductive, either impeding or letting current flow. When voltage is applied to the transistor's gate, it changes its state.
Transistors to Gates to Circuits to Systems
Transistors, as well as resistors, capacitors and diodes, are wired in patterns that make up logic gates. Logic gates wired in patterns make up circuits, and circuits wired in patterns make up electronic systems. To learn more about the transistor, see transistor concept and chip. See phototransistor and High-K/Metal Gate.
In an "enhancement mode" transistor, the semiconductor material normally acts as an insulator. In a digital circuit, it works like an on/off switch becoming conductive for a moment when it is pulsed with electricity. However, it can also function like a relay to amplify analog signals such as from an audio source, transferring a low voltage at the gate to a larger voltage at the drain.
The first transistors had five times the mass of an entire chip today. In 1954, Texas Instruments pioneered the commercial production of silicon transistors. See
When IBM announced the System/360 in 1964, its Solid Logic technology tied three transistors together. With the top of the module removed, you can see the three silvery transistors. This half-inch square space today can hold millions of transistors. (Image courtesy of International Business Machines Corporation. Unauthorized use not permitted.)
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