PURPOSE: To reduce the degradation of distortion characteristics at the time of gain control in the gain control amplifier circuit and the frequency converting circuit.

CONSTITUTION: In a differential amplifier circuit using field effect transistors 106 and 107 for control, the sources of two field effect transistors 113 and 114 for gain control to be inserted between the sources of transistors 106 and 107 are connected in common and a voltage terminal 116 is connected through a resistor 115 to the common connection point. By letting a DC current flow through the transistors 113 and 114 for gain control, the resistance value of a channel resistor between the drain and the source is stably changed to improve distortion characteristics.