For what portion of a cycle does a Class AB amplifier operate?

Amplifier classes are defined by their conduction angle, which is the portion of the 360-degree AC cycle during which the device amplifies. Class A conducts for the full 360 degrees, and Class B conducts for exactly half, or 180 degrees. Class AB is specifically designed to be a compromise between the high linearity of Class A and the better efficiency of Class B. By biasing the amplifier slightly above the cutoff point, it conducts for more than 180 degrees but less than 360 degrees. This slight overlap prevents the crossover distortion that occurs in pure Class B amplifiers when the signal transitions between the positive and negative halves of the cycle.