GAIN CONTROL AMPLIFIER

PURPOSE: To obtain an amplifier provided with a compensation circuit to reduce influence of fluctuation of temperature and signal level by providing a variable attenuator and generating a control signal by connecting a means to generate a reference signal with a means to generate an intermediate control signal. CONSTITUTION: A part of an input signal becomes the intermediate control signal as a second output of a coupler 14 in a detector 20. When the reference signal from a temperature compensation circuit 26 is provided with a second input of a differential amplifier (= operational amplifier) 24, the control signal is outputted from the operational amplifier 24. Amount of attenuation varying according to a change of the intermediate control signal is successively provided with the variable attenuator 16 by the control signal. When the reference signal is provided, the reference signal is set as proper voltage by a predetermined value of surrounding temperature and inputted as an invariable signal in the attenuator 16 by the amplifier 24. Specifically, even if a difference between the control signal and the intermediate control signal is measured, the proper control signal is supplied by the output of the amplifier 24. The control signal is supplied to a control port of the attenuator 16 and a predetermined amount is reduced.