Patent ID: 7642857

Claim:
A power amplifier, comprising: an output stage for amplifying a radio frequency (RF) signal, the output stage operably coupled to an output load; a bias circuit operably coupled to the output stage, the bias circuit capable of applying a bias voltage to the output stage, wherein the bias circuit comprises: a bias transistor having a base, a collector, and an emitter, the emitter of the bias transistor operably coupled to the output stage; a voltage circuit for setting a collector voltage of the bias transistor, the voltage circuit operably coupled to a voltage and to the collector of the bias transistor; and a plurality of diodes operably coupled in series between the base of the bias transistor and a ground; and a limit circuit operably coupled to the bias circuit for detecting an increase in the current of the output stage under an output load mismatch and in response, decreasing the bias voltage applied to the output stage.