PURPOSE: To make the package small by providing a conductor pattern forming an open stub of a double overtone wave suppressing circuit to a capacitor section so as to reduce the mount area.

CONSTITUTION: An open stub of a double overtone wave suppression circuit is formed respectively by conductor patterns 12A-12C on a dielectric board of a capacitor section 1 whose specific dielectric constant is far larger than that of a dielectric board of a microstrip line 2, and connected to output electrodes 31A-31D of a transistor chip 3 by metallic thin wires 7A-7D. In this case, let the operating frequency be 1GHz and the specific dielectric constant of the dielectric board of the capacitor section 1 be 100, then the physical length of the open stub corresponding to a double overtone wave with respect to an equivalent electric length, that is, 1/4 wavelength with respect to 2GHz is reduced to nearly 1/3 of the conventional physical length of the open stub.