Mixer with high linearity

A mixer, comprising:

• a transconductance stage comprising a first sub-transconductance stage receiving a first input signal through a first input node and outputting a first output signal through a first output node, and a second sub-transconductance stage receiving a second input signal through a second input node and outputting a second output signal through a second output node, wherein the first sub-transconductance stage comprises:
• a first transistor coupled between the first output node and a first power node, having a first gate coupled to the first input node, and operating in a saturation region;
• a second transistor coupled to the first power node, having a second gate coupled to the first input node, and operating in a sub-threshold region;
• a first biasing circuit providing a first bias voltage;
• and
• a third transistor coupled between the first output node and the second transistor, and having a third gate coupled to the first bias voltage;
• a first switching quad coupled to the first output node and the second output node, generating a first translation current according to the first output signal and the second output signal;
• a second switching quad coupled to the first output node and the second output node, generating a second translation current according to the first output signal and the second output signal;
• a first transimpedance amplifier transforming the first translation current to a first corresponding voltage;
• and
• a second transimpedance amplifier transforming the second translation current to a second corresponding voltage.