SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a circuit which can suppress a signal leas and which is suitable for handling a signal at a comparatively high frequency when a quadrature modulation means constituted of a MOS device is provided. SOLUTION: A circuit 1, a circuit 2, and a circuit 3 comprise a plurality of MOS device so as to be arranged on an SOS substrate. The substrate does not use a quard ring or a trench structure which is used in an integrated circuit which uses a bipolar or MOS transistor or an ordinary silicon substrate. A phase-shifting circuit 1, to which an Lo signal is input from the outside, outputs a sin signal and a cos signal whose phases are different by 90 deg.. A quadrature modulation circuit 2, to which the sin signal and the cos signal are input, modulates both signals by signals (I, the inverse of I, Q and the inverse of Q) from the outside, and it removes an image signal so as to output a modulation signal. An output buffer circuit 3 which has an AGC function and to which the modulation signal is input from the quadrature modulation circuit 2 outputs the modulation signal to an outside load whose impedance is comparatively low.