A buffer amplifier serves to isolate one part of a circuit from another, providing electrical impedance transformation from one circuit to another. There are two main types of buffers: voltage and current. Both are used, respectively, to transfer either voltage or current from a primary circuit with low output impedance to another circuit with high input impedance. The buffer amplifier, in between the two circuits, prevents the secondary circuit from loading the primary circuit and interfering with desired operation of the primary circuit. Amplifiers have enormous voltage gain, often use feedback of the output signal back to the input of the amplifier to operate, and can be classified in different ways. They can be identified by the device they are intended to drive (e.g., audio amplifier), the input that they are to amplify (e.g. sensing amplifier), the frequency range of the signal (e.g., RF, audio), and by the function that they perform (e.g. buffer amplifier, current-shunt amplifier.)
