Solid-state electronic component, made of
semiconductor material, with three or more
electrodes, that can regulate a current
passing through it. A transistor can act as
an amplifier, oscillator, photocell, or
switch, and usually operates on a very small
amount of power. Transistors commonly consist
of a tiny sandwich of germanium or silicon,
alternate layers having different electrical
properties. A crystal of pure germanium or
silicon would act as an insulator
(nonconductor). By introducing impurities in
the form of atoms of other materials (for
example, boron, arsenic, or indium) in minute
amounts, the layers may be made either
n-type, having an excess of electrons, or
p-type, having a deficiency of electrons.
This enables electrons to flow from one layer
to another in one direction only. Transistors
have had a great impact on the electronics
industry, and are now made in thousands of
millions each year. They perform many of the
same functions as the thermionic valve, but
have the advantages of greater reliability,
long life, compactness, and instantaneous
action, no warming-up period being necessary.
They are widely used in most electronic
equipment, including portable radios and
televisions, computers, satellites, and space
research, and are the basis of the integrated
circuit (silicon chip). They were invented at
Bell Telephone Laboratories in the USA in
1948 by John Bardeen and Walter Brittain,
developing the work of William Shockley.