To improve a power amplifier, capable of conducting gain switching suitable to GSM (global system for mobile communications)/EDGE (enhanced data rate for GSM evolution) modes, while suppressing the noise power of receiving bands.
An amplifier unit 28 of the power amplifier comprises a first to a third amplifier stage 422, 423 and 425 and a signal transfer unit 58, provided in parallel to the amplifier stage 422. When a control voltage Vmod2 is set to L level, an input signal IN1800 is amplified by the first to the third amplifier stage 422, 423 and 425, and the signal transfer unit 58 does not transfer a signal during this period. When a control voltage Vmod2 is set to H level, the signal transfer unit 58 transfers the input signal IN1800 to a transistor Tr2 via a diode D1. A Vmod1800 is set to L level during this period, and the amplifier stage 422 of the first stage is turned off, and power consumption is reduced.
SHIMURA TERUYUKI
ASADA TOMOYUKI
SUZUKI SATOSHI
