Apparatus for providing variable control of the gain of an RF amplifier

摘要

A method and apparatus for providing remote control of the output power level of an amplifier. The method uses pulse width or pulse density modulated signal proportional to the power level of the amplifier. This signal is detected and filtered to provide a control voltage to the apparatus mentioned below. The apparatus includes an amplifier, and a comparator having a first input coupled to an output terminal of the amplifier, a second input coupled to a control signal, and an output terminal coupled to an input terminal of the amplifier. The amplifier and comparator operate to form a feedback loop which functions to equalize the voltage level of an output signal present at the output terminal of the amplifier to the voltage level of the control signal. The equalization of the voltage level of the output signal of the amplifier to the voltage level of the control signal is effected by adjusting the drain current flowing through the amplifier. Accordingly, by varying the voltage level of the control signal, the power level of the output signal of the amplifier can be varied. <IMAGE>