Question

FM uses class______ amplifiers and AM uses class ______ amplifiers.

(a) C, C

(b) A, C

(c) C, A

(d) AB, C

The question was posed to me in unit test.

I'd like to ask this question from Frequency Modulation Vs. Amplitude Modulation in chapter Modulation Techniques for Mobile Radio of Wireless/Mobile

Answer 1

The correct choice is (c) C, A

For explanation: The constant envelope of the transmitted signal allows efficient class C amplifiers. However in AM, it is critical to maintain linearity between the applied message and amplitude of transmitted signal. Therefore, class A or AB are used for AM systems.