Patent ID: 8085008

Claim:
An apparatus comprising: a switch network having a first output terminal, a second output terminal, a plurality of input terminals, a common mode terminal, a first feedback terminal, and a second feedback terminal, wherein the switch network outputs a differential output signal though the first and second output terminals, and wherein the switch network outputs a common mode signal through the common mode terminal; an amplifier having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the amplifier is coupled to the common mode terminal so as to receive the common mode signal, and wherein the second input terminal of the amplifier receives a reference voltage; a first variable resistor that is coupled between the first feedback terminal and ground, wherein the magnitude resistance of the first variable resistor is based at least in part on an output signal from the output terminal of the amplifier; a second variable resistor that is coupled between the second feedback terminal and ground, wherein the resistance of the second variable resistor is based at least in part on the output signal from the output terminal of the amplifier; and an adjustable current source that is coupled between the first and second feedback terminals, wherein the magnitude of the current from the adjustable current source is based at least in part on the output signal from the output terminal of the amplifier.