Linearization Techniques for Push-Pull Amplifiers

Amplifiers that need to drive heavy loads (low resistances and/or large capacitances) with good efficiency generally use a push-pull output stage. This intrinsically creates large open-loop distortion components that need to be compressed through feedback to insure high closed-loop linearity. Minimizing close loop residual distortion involves three steps that will be discussed in this chapter. Eliminate all open-loop source of distortion not intrinsic to the proper operation of the push pull structure. Second, choose the amplifier topology that gives the maximum close loop compression of the open-loop distortion components for a given bandwidth. Third, maximize the open-loop gain in the signal band and/or the unity gain bandwidth of the amplifier for a given topology while insuring stability in the presence of variable loads.