There is provided a power control circuit having a stable high-speed
operation, and a semiconductor device and a transceiver circuit using it.
The power control circuit controls the gain of an amplifier so that power
outputted from the amplifier reaches a desired value according to a
digital control signal. The power control circuit includes a digital
feedback loop which converts a detected signal obtained by detecting a
value of the output power of the amplifier to a digital signal,
determines a differential between the digital signal and the digital
control signal, converts the differential to an analog signal and outputs
a first feedback signal, an analog feedback loop which outputs a high
frequency element corresponding to a differential between an analog
signal to which the digital control signal is converted and the detected
signal, as a second feedback signal, and an adder which determines the
sum of the first and the second feedback signal and outputs a gain
control signal for controlling the gain of the amplifier.