What is common collector?

A common collector, also known as an emitter follower, is a basic transistor amplifier configuration where the collector terminal is common to both the input and output. In this setup, the input signal is applied between the base and the emitter, while the output is taken from the emitter. This configuration provides high input impedance and low output impedance, making it useful for impedance matching and signal buffering. Additionally, it offers voltage gain close to unity, meaning the output voltage closely follows the input voltage.