A class AB amplifier is a combination of both class A and B in that the output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of class A designs, but enough to keep each device operating so they respond instantly to input voltage demands. Thus the non-linearity of class B designs is eliminated, without the inefficiencies of the class A design.