Patent ID: 7973587

Claim:
A transconductor for use in a mixer, comprising: a first resistor, and a second resistor; a differential amplifier, comprising a first input end, a second input end, a first output end, and a second output end; wherein, a differential voltage signal is inputted to the first input end and the second input end via the first resistor and the second resistor, respectively; a first feedback circuit, provided between the first output end and the first input end; a second feedback circuit, provided between the second output end and the second input end; a first transistor, having the gate thereof coupled to the first output end of the differential amplifier; wherein the first output end outputs a first output signal for controlling a first current passing through the first transistor; and a second transistor, having the gate thereof coupled to the second output end of the differential amplifier; wherein the second output end outputs a second output signal for controlling a second current passing through the second transistor, and the first current and the second current determine a differential current, wherein the first feedback circuit comprises a third transistor, which has the gate thereof coupled to the first output end of the differential amplifier and forms a first current mirror with the first transistor; and the second feedback circuit comprises a fourth transistor, which has the gate thereof coupled to the second output end of the differential amplifier and forms a second current mirror with the second transistor, wherein the first feedback circuit further comprises a third resistor coupled between the third transistor and the first input end; and the second feedback circuit further comprises a fourth resistor coupled between the fourth transistor and the second input end, and wherein the first and second feedback circuits assist the transconductor in providing linear transconductance.