Which of the following classes of amplifier provides the highest efficiency?

Amplifier efficiency is closely related to the conduction angle, which is the portion of the input signal cycle during which the amplifier's active device conducts current. A Class C amplifier is biased well beyond cutoff, meaning it conducts for less than 180 degrees of the input cycle. Because the device is turned off for the majority of the time, it wastes very little power as heat. This allows Class C amplifiers to achieve the highest theoretical and practical efficiency, often exceeding 75%. In contrast, Class A, AB, and B amplifiers conduct for longer portions of the input cycle. While this improves the linearity of the output signal, it results in a higher average current draw and significantly lower efficiency.