Self on Audio, 3rd Edition

Chapter 23Distortion in power amplifiers

Part II: the input stage (Electronics World, September 1993)

The input stage of a power amplifier only has to handle small signals compared with the output signal, and so it might be thought that its contribution to the distortion of a complete power amplifier would be negligible. This is not so.

The vast majority of amplifiers use Miller dominant-pole compensation, in which a small capacitor essentially turns the VAS stage into an integrator. This gives very dependable stability, and has many other advantages, but the downside is that as the frequency increases, the amount of current that has to be pumped in and out of the Miller capacitor increases proportionally. Therefore the error voltage across ...