Automatic volume control - has proportional plus integral DC control loop and capacitor controlled by parallel input cct.

摘要

The output of a microphone (10) is amplified (12) and the output fed to a rectifier (14) generating an input (Ve) to the control circuit (16). The control circuit consists of an operational amplifier (24) with a parallel circuit coupled to the inverted input. The parallel circuit consists of a 1M ohm resistor (20) in parallel with a diode (21) and a series of 100 K ohm resistor (22). A 0.5 mu f capacitor (26) is coupled around the operational amplifier and the positive input supplied with a reference (U soll). The output from the amplifier (Ua) provides a control reference for the A.C. amplifier (12). Due to the inclusion of the diode (21) a shorter time constant is associated with the capacitor charging that with the discharge.