A common collector is a type of transistor amplifier configuration, often used in electronic circuits. In this setup, the collector terminal of the transistor is connected to a fixed voltage, while the input signal is applied to the base. The output is taken from the emitter, making it a voltage follower that provides high input impedance and low output impedance. This configuration is commonly used for impedance matching and signal buffering. It allows the circuit to drive loads without significantly affecting the input signal. The common collector is also known as an emitter follower due to its output following the input voltage closely.