Patent ID: 8515367

Claim:
A transmission circuit including a high-frequency power amplifier which has, as an operation mode, a nonlinear mode in which the high-frequency power amplifier operates as a nonlinear amplifier, and a linear mode in which the high-frequency power amplifier operates as a linear amplifier, the high-frequency power amplifier outputting a transmission signal, the transmission circuit comprising: a mode setting section that switches the operation mode to either the nonlinear mode or the linear mode in accordance with a set power level of the transmission signal; a signal generation section that converts an input signal into first and second signals in accordance with a mode signal which includes information regarding the operation mode set by the mode setting section; a power voltage control section that applies a power voltage corresponding to the first signal to the high-frequency power amplifier; a variable gain amplifier that amplifies the second signal; a detection section that detects a power level of the second signal amplified by the variable gain amplifier; and a first gain setting section that sets, irrespective of the operation mode, a gain of the variable gain amplifier to a value, which enables the variable gain amplifier to operate linearly and corresponds to a comparison result obtained through comparison between the detected power level and a target power level of the variable gain amplifier corresponding to the set power level.