TRANSMISSION CIRCUIT

摘要

A transmission circuit (100) is provided with an RF-IC (110), an EM-IC (120), and a power amplifier (130). The EM-IC (120) is provided with a DC/DC converter (123), a transistor (124), a low drop out regulator (121), and a regulator output changeover switch (122). After the elapse of a predetermined period, which is the period until a quadrature modulation mode power source voltage that a DC/DC converter (123) outputs becomes stable at a desired value when the operation mode of the transmission circuit is switched from a polar modulation mode to a quadrature modulation mode, the regulator output changeover switch (122) switches the connection destination of the gate of the transistor (124) to a fixed potential and outputs, as a control voltage, the quadrature modulation mode power source voltage that the DC/DC converter (123) outputs.