Question

Which type of power amplifier has the highest theoretical efficiency?

• A. Class A
• B. Class B
• C. Class AB
• D. Class C

Hint:

Efficiency order → Class C>Class B>Class AB>Class A.

Answer 1

The Correct Option is D

Concept: Power amplifiers are classified based on their conduction angle and efficiency. Efficiency refers to how much of the input power is converted into useful output power.
Step 1: Understanding amplifier classes.

• Class A: Conducts for full cycle (360°), low efficiency (~25--30%)
• Class B: Conducts for half cycle (180°), moderate efficiency (~78.5%)
• Class AB: Between Class A and B
• Class C: Conducts for less than 180°

Step 2: Efficiency comparison.
Class C amplifiers have the highest theoretical efficiency (can exceed 80--90%) because they conduct for a very small portion of the input cycle.
Step 3: Limitation.
They introduce significant distortion and are mainly used in RF applications where tuned circuits are employed.
Step 4: Conclusion.
Thus, Class C amplifiers have the highest theoretical efficiency.