In common-collector amplifier the input is given at the base and the output is taken at the emitter. It is called the common-collector configuration because (ignoring the power supply battery) both the signal source and the load share the collector lead as a common connection point. In this amplifier, there is no phase inversion between input and output. The input impedance of the CC amplifier is very high and output impedance is low. The voltage gain is less than unity. This amplifier is used for impedance matching and as a buffer amplifier. This circuit is also known as emitter follower.