Deep Dive: G7B02
The correct answer is D: Class C. The class of amplifier that has the highest efficiency is Class C. Class C amplifiers conduct for less than 180° of the input cycle, making them very efficient but only suitable for constant-envelope signals like FM or CW. For amateur radio operators, this is important for high-power operation. Understanding this helps when selecting amplifier classes.
Why Other Answers Are Wrong
Option A (Class A): Incorrect. Class A has low efficiency (typically 25-50%) - it conducts for 100% of the cycle, wasting power. Class A is least efficient. Option B (Class B): Incorrect. Class B has moderate efficiency (typically 50-78%) - it conducts for 50% of the cycle. Class B is more efficient than A but less than C. Option C (Class AB): Incorrect. Class AB has moderate efficiency (typically 50-65%) - it conducts for more than 50% but less than 100%. Class AB is more efficient than A but less than C.
Exam Tip
Highest efficiency amplifier = Class C. Think 'C'lass 'C' = 'C'onducts 'C'omparatively less = 'C'omparatively efficient. Class C conducts for less than 180°, making it most efficient. Not Class A (lowest), not Class B/AB (moderate) - just Class C (highest).
Memory Aid
Highest efficiency amplifier = Class C. Think 'C'lass 'C' = 'C'onducts less = 'C'omparatively efficient. Class C conducts for less than 180°, making it most efficient. Highest efficiency but only for constant-envelope signals.
Real-World Example
You need a high-efficiency amplifier for FM operation. Class C amplifiers conduct for less than 180° of the input cycle, making them very efficient (typically 70-90%). However, Class C only works for constant-envelope signals (FM, CW) - it can't be used for SSB or AM. Class C has the highest efficiency.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G7B
Reference: 2023-2027 Question Pool · G7 - Practical Circuits
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G7B topic.