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Abstract

A mixer circuit with common-mode noise rejection combines input signals into a single output signal in a predetermined ratio and reduces the effect of noise within the single output signal. The input signals and their respective ground signals are all coupled to the mixer circuit. The mixer circuit eliminates common-mode noise within the output signal, caused by each input signal having a different ground reference signal, by passing each input signal differentially with its respective ground reference signal to a standard Gilbert Cell. Mixer control signals are coupled as control inputs to the Gilbert Cell for controlling the ratio of the input signals included in the output signal. The Gilbert Cell receives the differential input signals and outputs a differential output signal comprised of a predetermined ratio of the input signals as specified by the control signals. The differential output signal is then converted to a single ended output signal. After being converted to a single ended output voltage, the single ended output signal is passed through an output buffer and provided as the output signal. Each of the differential input signals are generated by a transconductance stage and provided to differential pairs within the Gilbert Cell. The output signal is also provided to each transconductance stage as a feedback signal.

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