AGC is derived in a receiver from one of two circuits. Depending on the method used, it is called:

In modern receivers, the control voltage for the AGC can be sampled from either the intermediate frequency (IF) stage or the audio stage (after demodulation). IF-derived AGC samples the signal before the detector, offering fast response and excellent control, especially for AM signals. Audio-derived AGC samples the signal after the detector, which is a simpler design often used in SSB/CW receivers. Options suggesting RF-derived AGC are incorrect because the RF stage is too broad and precedes the main selectivity filters; the receiver must base its AGC action on the specific narrowband signal being listened to.