Patent ID: 7057458

Claim:
A balanced power amplifier comprising: a voltage source; a first power amplifier element including at least a grounded-emitter first bipolar transistor; a second power amplifier element including at least a grounded-emitter second bipolar transistor; a first variable impedance element, one end of which is electrically connected to a base side of the first bipolar transistor; a second variable impedance element, one end of which is electrically connected to a base side of the second bipolar transistor; a two-terminal regulator circuit connected to between the first variable impedance element and the second variable impedance element; a first resistance connected to between a first node disposed between the first variable impedance element and the regulator circuit and the voltage source; a second resistance connected to between a second node disposed between the second variable impedance element and the regulator circuit and the voltage source; a first input terminal connected to a third node disposed between a base side of the first bipolar transistor in the first power amplifier element and the first variable impedance element; and a second input terminal connected to a fourth node disposed between a base side of the second bipolar transistor in the second power amplifier element and the second variable impedance element, wherein the first and second power amplifier elements are driven in parallel and in opposite phase.