Takes a low-impedance output and turns it into a high-impedance output without changing the voltage or the phase.
Also known as unity gain amplifier because the output follows the input.
Fundamentals of Electric Circuits, 5th Edition by Charles K. Alexander and Matthew N. O. Sadiku
Provides a gain of unity with no polarity or phase reversal.
Electronic Devices and Circuit Theory, 11th Edition by Robert L. Boylestad & Louis Nashelsky