PURPOSE: To obtain an excellent temperature characteristic by setting a constant voltage source to a prescribed value so as to apply excellent temperature compensation to the mixer gain.

CONSTITUTION: The mixer circuit consists of two pairs of upper-stage differential transistors(TRs) Q3∼Q6 receiving a local signal and a couple of lower stage differential TRs Q7, Q8 receiving a mixer signal and the lower stage differential TRs Q7, Q8 are biased by a constant voltage source V1 independently of temperature. Then the value V1 of the constant voltage source V1 is set to satisfy equation I to make the mixer gain independent of temperature, where T is the absolute temperature and VBE is a base-emitter voltage of a TR in equation I. Thus, the temperature compensation of the mixer gain is implemented excellently.