Class C amplifiers, topology shown in figure 4, have zero idle bias current at the
output, which makes them similar to Class B. What makes Class C different from
Class B is that Class C has an area where the idle current is zero, which is more than
50% of the total supply voltage. Therefore there is even more distortion caused by
crossover of source and sink currents then in Class B. This distortion causes poor
sound quality and makes Class C amplifiers inadequate for audio applications.
Theoretically the maximum efficiency for a Class C amplifier is 100% at zero output
but 78.5% at full output.