Patent ID: 8346187

Claim:
A transmission circuit that outputs a transmission signal having a power level indicated by a power level signal which is transmitted from a predefined base station, the transmission circuit comprising: an amplitude phase separator that separates an input signal into an amplitude signal that indicates an amplitude component and a phase signal that indicates a phase component a phase modulator that conducts a phase modulation on the phase signal and outputs a phase modulation signal; a power amplifier which (i) includes a transistor, (ii) amplifies the phase modulation signal using the transistor and (iii) outputs the amplified phase modulation signal as the transmission signal; a collector controller that controls a collector voltage supplied to the transistor; a base controller that controls a base bias voltage supplied to the transistor; and a switching controller, which (i) receives the power level signal from the predefined base station, (ii) switches, when the power level indicated by the power level signal is lower than a predefined value, to control the collector controller in accordance with the amplitude signal and the power level signal and to control the base controller in accordance with the power level signal, and (iii) switches, when the power level indicated by the power level signal is equal to or more than the predefined value, to control the base controller in accordance with the amplitude signal and the power level signal and to control the collector controller in accordance with the power level signal, wherein the power amplifier amplifies the phase modulation signal based on the collector voltage and the base bias voltage controlled by the collector controller and the base controller.