AVC Automatic Volume Control Circuit

Posted on Feb 4, 2014

The function of this automatic volume control circuit is to amplify signals without distorting its dynamic compression. The amplitude differences in the signal are levelled off and the disturbing effect vanish. With this tehnique, overcompensation in the volume is avoided. The circuit is used to automatically control the volume levels of cassette

AVC Automatic Volume Control Circuit
Click here to download the full size of the above Circuit.

recorders, audio tape recorders, amplifiers or radio devices. The AVC circuit works this way: the FET (t1) is used as a variable resistor. The resistance between the drain and source of T1 can be between 150 © and infinite. It is parallel resistor to R2 and togheter with R3 controls the gain of OP amp A1 (around 20 dB). The following OP amp A2 is wired as an amplifier with P1 as its gain control. The negative part of the output signal coming from A2 is rectified and fed to the gate of T1. Small variations on the signal amplitude does not influence the amplification since the FET has a short delay caused by R6. The opposite effect is also slow because of the discharge time of C1. Both effects result to a smooth regulation of the signal amplitude, making this automatic volume control circuit so effective. The signal voltage at the gate of T1 must be as low as possible to influence the drain-source resistance. To achieve this, the voltage divider R1, R4 is set at the input line to attenuate the signal by 40 dB. This tehnique enables signals up to 1 Veff to be processed without a problem and with distorsions level below 0. 5%. The signal-noise ratio is over 70dB by an input voltage of 1Veff. The losses at the attenuator is compensated by the amplification through Ai and IC2. The high pass filter made of C2, R7 prevents the bass signals from influencing the regulation. With proper dimensioning of these components, the cutoff...

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    LM317 Regulator Circuit
    Biasing Op-Amps into Class A
    Sample-And-Hold Circuit Ii Circuit
    Battery Level Monitor Circuit
    power supply Transistor current limiter microcontroller controlled
    RC5 Repeater
    Battery simulator provides current limiting
    The many DC to DC converters using IC-555
    12 Volt fluorescent lamp drivers
    LM4819 audio power amplifier circuit
    Using music integrated circuit delay lamp
    Light emitting diode LED displays the basic structure of the driving circuit