AUTOMATIC GAIN CONTROL

摘要

In the automatic gain control apparatus including two variable amplifier 3 connected in serial and amplifying an input signal; two fixed amplifier connected in serial at an output edge of the variable amplifier 3; a signal distributor 9 for distributing the output of the fixed amplifier 8; a high frequency signal detector 11 for detecting the high frequency signal distributed from the signal distributor 9; a differential integrator 13 for inputting the output of the high frequency signal detector 11 and a reference signal and comparing, and outputting the control signal to control an output frequency to two variable amplifier 3 according to the comparing result, the apparatus further comprises: a low frequency signal detecting means 15 for inputting the reference low frequency signal to obtain a wanted output frequency through a cable from an operator, detecting a DC level value from the inputted low frequency signal, and outputting the reference signal input unit of the differential integrator 13; and a bidirectional clamping means 19 connected to the output unit of the differential integrator 13 for preventing a control voltage having less or more than reference value.