Gain compensation circuit

摘要

A circuit for compensating for GaAs FET amplifier gain variations over a frequency band as a function of temperature. The circuit includes a passive equalizer circuit having a fixed gain over the frequency band and an active equalizer circuit having a gain which varies over the frequency band as a function of temperature. The passive and active equalizers are coupled in series. The active equalizer circuit comprises varactor diodes in a low pass filter arrangement with the bias voltage of the varactor being provided by an external driver controlled by a temperature sensitive thermistor. As the value of the varactor's junction capacitance is increased (as a function of the temperature controlled bias voltage), the cutoff frequency of the low pass filter decreases.