Patent ID: 8514969

Claim:
An amplitude control circuit that is used for a polar modulation transmission circuit, the amplitude control circuit comprising: a digital-to-analog converter that converts amplitude data into a differential amplitude signal and outputs a result; a level control section that controls level of the differential amplitude signal output from the digital-to-analog converter, according to transmitting power information that shows output power of the polar modulation transmission circuit; a first offset calculation section that applies a direct current offset to match the transmitting power information to the differential amplitude signal output from the level control section; a differential single conversion section that performs differential single conversion to a differential amplitude signal output from the first offset calculation section and outputs a result; a reference voltage generation section that supplies a reference voltage to the differential single conversion section; and a reference voltage adjusting section that calculates gain from the digital-to-analog converter to the first offset calculation section, by detecting output of the first offset calculation section, adjusts the reference voltage from the reference voltage generation section in order to make a value of the gain to be a defined value, and supplies a result to the digital-to-analog converter and the first offset calculation section.