US Patent 8432228 Power control circuit for radio frequency power amplifiers

A power control circuit for regulating an output voltage applied to a radio frequency power amplifier. The power control circuit includes an amplifier, a pass transistor and one or more saturation detectors. An input ramp voltage having a magnitude equal to a first voltage level is applied to a negative terminal of the amplifier. The pass transistor provides an output voltage at a drain terminal of the pass transistor. The saturation detector detects a magnitude of a voltage at a gate terminal of the pass transistor and generates a control current based on the magnitude of the voltage at the gate terminal of the pass transistor. The voltage regulating circuit reduces the magnitude of the input ramp voltage from the first voltage level to a third voltage level based on the control current.