At the heart of a transistor is a diode junction, which consists of a piece of n-type semiconductor and a piece of p-type semiconductor.
you want to find out more about the way electric fields behave in the boundary
layer between n-type and p-type materials, and what is meant by doping, have a
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have here a p-n junction.
A bipolar transistor consists of two p-n junctions back to back like this:
arrows represent conventional
current flowing from positive to negative. Semiconductors are doped so that some
have an excess
of electrons, n-type
material, while others have a deficiency
of electrons called holes.
These are found in p-type
conduct when the base-emitter voltage is about 0.7
V. Transistors are current controlled devices. The bigger the
base emitter current, the bigger the collector emitter current.
The transistor can be used as an amplifier or a solid state switch.
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