LM307 voltage-controlled gain amplifier circuit

Published:2011/7/4 0:28:00 Author:John | Keyword: gain amplifier | From:SeekIC

Voltage-controlled gain amplifier can be composed of approximate logarithmic relationship between the FET gate voltage and drain - source resistance RSD. The integrated circuit uses chip LM307 as an amplifier and uses inverting input form. According to figure (a), RSD and R1 form the voltage divider circuit (to divider pressure for Vi). The plus of 4 1N914 diodes’ voltage drop and the resistor R5’s voltage drop is equal to FET’s gate voltage VG. The VG is with the nonlinear relationship with the control voltage VC, but the correlation between the control voltage VC and the amplifier‘s gain attenuation is shown in figure (b) below.



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