Automatic gain control circuit

摘要

In a laser scanning system, an automatic gain control (AGC) circuit for dynamically adjusting the gain of a receiver that is used to receive light reflected from a bar code. The AGC provides a fast adjustment to receiver gain so that the receiver can provide a decodable signal quickly. To accomplish the fast adjustment, the AGC circuit, in addition to sensing the final output of the receiver, includes an additional feedback path from an amplifier in the receiver that is located before the final amplification stage. The additional feedback has a negligible attack time, and adjusts receiver gain quickly, thereby minimizing the time required to reach steady state.