Patent ID: 8922281

Claim:
A power amplifier comprising: an RF signal input terminal; a first amplifier device; a second amplifier device; a load device; a first switch circuit; a second switch circuit; and an impedance adjusting circuit; wherein a common electrode of the first amplifier device and a common electrode of the second amplifier device are connected to a ground potential, and an output electrode of the first amplifier device and an output electrode of the second amplifier device are connected to the load device; the first switch circuit, in response to a power mode signal at a first voltage level, supplies an RF input signal of the RF signal input terminal to an input electrode of the first amplifier device and to an input electrode of the second amplifier device so that the first amplifier device and the second amplifier device perform parallel amplification operations on the RF input signal; the first switch circuit, in response to the power mode signal at a second voltage level different from the first voltage level, supplies the RF input signal of the RF signal input terminal to the input electrode of the first amplifier device and substantially stops supplying of the RF signal to the input electrode of the second amplifier device so that the first amplifier device performs a stand-alone amplification operation on the RF input signal; one end of the impedance adjusting circuit is connected to a connection node between the output electrode of the first amplifier device and the output electrode of the second amplifier device, the other end of the impedance adjusting circuit is connected to one end of the second switch circuit, and the other end of the second switch circuit is connected to the ground potential; the impedance adjusting circuit includes a reactance element connected between the one end and the other end of the impedance adjusting circuit; and the second switch circuit causes the one end and the other end of the second switch circuit to be electrically disconnected from each other in response to the power mode signal at the second voltage level, and causes the one end and the other end of the second switch circuit to be electrically connected to each other in response to the power mode signal at the first voltage level.