PURPOSE: To increase the gain at reduction in a power supply voltage Vcc (in operation of AGC interrupt circuit) and to make the gain constant by constituting the AGC interrupt circuit to make the gain constant at a drop of the power supply voltage with an operational amplifier.
CONSTITUTION: When a power supply voltage Vcc is a normal voltage (or the normal voltage or over), an L level is inputted to an AGC interrupt circuit control signal input 4, AGC interrupt circuits 2,3 are stopped and the circuit acts like the usual AGC amplifier circuit. When the power supply voltage Vcc drops, an H level is inputted to the AGC interrupt circuit control signal input 4, the AGC interrupt circuits 2,3 are operated, an AGC input to an operational amplifier 1 of the AGC amplifier circuit is constant (Vref) to make the gain of the AGC amplifier circuit constant. An operational amplifier 2 is employed for the AGC interrupt circuit section to decrease the remaining voltage at the operation of the AGC interrupt circuit is as small as an offset voltage (nearly several mV) of the operational amplifier and a leakage current at the stop of the AGC interrupt circuit is eliminated.
ARAYA YUKIHIRO
KATO NAOYUKI
MITSUBISHI ELECTRIC CORP
| JPS6447111A | 1989-02-21 | |||
| JPS61170107A | 1986-07-31 | |||
| JPS62120706A | 1987-06-02 | |||
| JPH0193731A | 1989-04-12 |