Patent ID: 7132888

Claim:
A gain circuit, comprising: a substrate; a first differential pair amplifier disposed upon the substrate and coupled to a first circuit output having a gain contributing to circuit gain in direct proportion to the first differential pair amplifier gain; a second differential pair amplifier disposed upon the substrate and coupled to a second circuit output having a gain, and coupled to the first differential amplifier such that an increase in second differential pair amplifier gain contributes to a decrease in the circuit gain; and a variable voltage source coupled to the circuit outputs, a voltage output of the variable voltage source determining respective drain source voltages on the first differential pair and the second differential pair based on a differential input signal received at the first differential pair amplifier and the second differential pair amplifier, and thereby controlling the gain of the first differential pair and the gain of the second differential pair, wherein the variable voltage source controls a transconductance of the gain circuit so as to improve linearity of the gain circuit.