Patent ID: 7064614

Claim:
An electronic circuit comprising: a power amplifier having a radio frequency (“RF”) power transistor for amplifying radio frequency signals such that a quiescent DC collector current in the RF power transistor is approximately constant over an operational range of collector voltages supplied from a collector power supply; a power amplifier bias transistor that biases the RF power transistor; a current mirror bias transistor having an operating area such that the current mirror bias transistor has substantially a same current density as the power amplifier bias transistor when the current mirror bias transistor and the power amplifier bias transistor are biased from a reference voltage supply that supplies a reference voltage controlling an output power of the power amplifier and remains approximately constant as the collector voltage varies through the operational range; a current mirror transistor biased by emitter current from the current mirror bias transistor and having an operating area such that a quiescent DC collector current density is about equal to a quiescent DC current density of the RF power transistor; and a first base ballast resistor and a second base ballast resistor, the first base ballast resistor placed between an emitter of the current mirror bias transistor and a base of the current mirror transistor and having a resistance for a voltage drop that is about equal to a voltage drop across the second base ballast resistor placed between an emitter of the power amplifier bias transistor and a base of the RF power transistor.