Figure 1 shows the essential components of a basic automatic gain-control (AGC) loop: the dc reference signal, VREF, establishes the output amplitude set-point; the output-measurement circuit obtains a running measure of the output level, based on a property (peak, average, rms, etc.) of the output signal; a comparator, derives a control signal; and a gain-adjustment circuit, applies enough distortionless gain or attenuation to the input signal to maintain the output level sufficiently close to the reference value. Read full article
