Circuit automatically adjusting gain of differential amplifier

PROBLEM TO BE SOLVED: To provide a circuit automatically adjusting the gain of a diffenteial amplifier which is satisfactory operated even when ununiform signal is amplified. SOLUTION: The circuit is provided with a duplex half wave rectifier(DHWR) connected tot he output of the differential voltage gain amplifier(VGA) generating two quantities depending on the amplitude of the half wave of the output signal of the amplifier(VGA), two compactors (COMP1 and COMP2) respectively provided with reference inputs (IN-1 and IN-2) for generating the output signal of each when inputs (IN+1 and IN+2) connected to the output (OUT1 and OUT2) of this rectifier (DHWR) and the amplitudes of the respective half eaves become larger than a level impressed to reference inputs (IN-1 and IN-2), and processing means (str1, A1, R1, Str2, A2, R2 and C) generating signals for the gain adjustment of the amplifier depending on the duration time of the output signal of the two compactors. COPYRIGHT: (C)1997,JPO