PURPOSE: To isolate terminals of the mixer and to reduce distortion by connecting a 6th capacitor whose other terminal is connected ground to an anode of a 1st or a 3rd diode.

CONSTITUTION: One terminal of a capacitor 21 whose other terminal is connected ground is connected to a connecting point between a capacitor 8 and an anode of a diode 4. In this case, the capacitor 21 is employed to avoid impedance unbalance which might be caused when the mixer is mounted in a form of a printed circuit board. Moreover, the capacitor 21 connecting to the connecting point between the capacitor 8 and the anode of the diode 4 may be connected to a connecting point between a capacitor 11 and an anode of the diode 4. Thus, the unbalanced impedance is cancelled and the isolation between terminals of the mixer is improved and deterioration is reduced.