Question
Which of these classes of amplifiers has the highest efficiency?
Answer Options
- A) Class A
- B) Class B
- C) Class AB
- D) Class C
Correct Answer: D
Explanation
The class of an amplifier is defined by the portion of the input signal cycle during which the amplifying device (transistor or tube) conducts current. Efficiency is the ratio of output power to DC input power.
Class C amplifiers conduct current for significantly less than half of the input signal cycle (less than 180^\circ). Because the device is off for most of the time, very little DC power is wasted as heat, making the Class C design the one that has the highest efficiency (theoretically up to 100\%). However, Class C is non-linear and is only suitable for constant-envelope modes like Frequency Modulation (FM) or CW.
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