Which statement about Automatic Gain Control (AGC) is true?

• A. AGC always increases gain with stronger signals
• B. AGC lowers noise figure by itself
• C. AGC adjusts gain to maintain a constant output level despite changing input signal strength
• D. AGC eliminates interference from adjacent channels

Answer: (C)

Automatic Gain Control is about keeping the output level stable as the input signal strength varies. It works by boosting gain when the received signal is weak so the output stays readable, and reducing gain when the signal is strong to prevent distortion or overload. This keeps the downstream stages, like the detector or demodulator, operating in a comfortable, linear range. It doesn’t inherently reduce the noise figure; noise figure is a property of the front-end noise and isn’t improved just by turning the gain up or down. It also doesn’t remove interference from adjacent channels—that’s handled by filtering and selectivity, not by gain control. So the true statement captures the purpose: adjusting gain to maintain a constant output level despite changing input strength.