Abstract: A radio frequency power amplifier is frequently provided with a feedback circuit to maintain the output power of the amplifier at a predetermined level. When the load connected to the amplifier changes, the feedback circuit causes the amplifier to produce the amount of power needed to maintain the predetermined level of power. If additional power is produced, it may be large enough to damage or destroy the amplifier and other circuits. A protection circuit is provided to prevent this. The protection circuit uses a differential amplifier having a first input provided by an output power sensor, a second input provided by a reference voltage, and an output for controlling the supply power to the radio frequency power amplifier. The two inputs are adjusted so that the differential amplifier becomes saturated when the sensed output radio frequency power is at some selected safe level above the normal output power level.