An electronic device made of semiconductor
material that can amplify electrical signals. The material, such as silicon
or germanium, is "doped" with minute amounts
of phosphorus, arsenic,
or antimony to produce n-type
material, in which current is carried by negative charges, electrons;
or with aluminum, gallium,
indium to give a p-type material.
Joining together a piece of each produces a diode. Sandwiching one type
between two of the other produces a transistor. These can thus be of two
kinds: a p-n-p or n-p-n transistor. The middle region
is known as the base, one of the side regions as the emitter and the other
as the collector. In an n-p-n transistor, the signal to be amplified
is fed across the collector, maintained at a constant voltage with respect
to the base. The amplified signal comes out across the base and the emitter.
|Geometric symbols for transistors (A) with n-type
base; (B) with p-type base
Transistors were first developed in 1948 by John Bardeen,
Walter Brattain, and William Shockley,
making possible many advances in technology, especially in computers,
portable radios and televisions, satellites,
industrial control systems, and navigation.