2015-08-21
288
A transistor is a three terminal semiconductor device. It can be
represented by the one common symbol shown below.
Note the names of each terminal. Having three terminals means that there are
several ways of connecting the transistor into a circuit, but by far the most
common is the common emitter configuration. In this configuration the base
is used as the input, the collector as the output and the emitter forms a common
terminal between input and output. With this arrangement the transistor acts as
an amplifier, providing both current and voltage amplification. Figure underneath shows a typical common emitter amplifier circuit.
We shall make no attempt to explain the operation of this circuit in this case; for our purposes an understanding is not required. We are going to adopt a 'systems' approach, where the amplifier is merely represented by a 'black box'.
