The COMMON-EMITTER CONFIGURATION (CE) is the most frequently used configuration
in practical amplifier circuits, since it provides good voltage, current, and power gain. The input to the CE
is applied to the base-emitter circuit and the output is taken from the collector-emitter circuit, making the
emitter the element "common" to both input and output. The CE is set apart from the other configurations,
because it is the only configuration that provides a phase reversal between input and output signals.
The COMMON-BASE CONFIGURATION (CB) is mainly used for impedance matching, since it
has a low input resistance and a high output resistance. It also has a current gain of less than 1.
In the CB, the input is applied to the emitter, the output is taken from the collector, and the base is
the element common to both input and output.