Patent ID: 7499693

Claim:
A mixer of a homodyne radio frequency (RE) receiver, which is made from a CMOS process, comprising: a gain stage, receiving a differential-typed RF signal and generating a first gained signal; a switch stage, used for mixing said first gained signal and a local oscillation (LO) signal to direct down-convert into a modulated signal; and a load stage, comprising a pair of first transistors, an impedance element and a pair of second transistors, the pair of first transistors providing a low impedance to permit said modulated signal entering the load stage, the impedance element having a first gain coefficient, the pair of second transistors providing a high impedance to resist signals, the load stage converting the modulated signal to a second gained signal according to the first gain coefficient, wherein the second transistor is a vertical npn bipolar junction transistor (BJT), which is parasitically formed on a MOS structure.