What is characteristic of an emitter follower (or common collector) amplifier?

An emitter follower, also known as a common collector amplifier, is a configuration where the output signal is taken from the emitter terminal. It has a voltage gain of approximately 1 (unity), meaning the output voltage closely 'follows' the input voltage in both amplitude and phase. Therefore, the input and output signals are in-phase. Emitter followers are widely used because they offer a high input impedance and a low output impedance, making them excellent buffer amplifiers for impedance matching. Distractors claiming phase inversion or low input impedance describe a common emitter configuration instead.