Patent ID: 7602220

Claim:
A system comprising: a first voltage input; a second voltage input; a first voltage-to-current converter comprising: a first circuit configured to provide a virtual ground, an input resistor R p disposed between the first voltage input and the virtual ground, and a circuit configured to generate an output current I outp responsive to current flowing through the resistor R p ; a second voltage-to-current converter comprising: a second circuit configured to provide the virtual ground, an input resistor R n disposed between the second voltage input and the virtual ground, and a circuit configured to generate an output current I outn responsive to current flowing through the resistor R n ; a third voltage-to-current converter comprising: a third circuit configured to provide the virtual ground, an input resistor R cmp disposed between the first voltage input and the virtual ground, an input resistor R cmn disposed between the second voltage input and the virtual ground, and a circuit configured to combine currents flowing through the input resistors R cmp and R cmn , and to generate an output current I Rcm proportional to the combined currents; and a circuit configured to provide the output current I Rcm to the first voltage-to-current converter and the second voltage-to-current converter so as to compensate for a common-mode voltage between the first voltage input and the second voltage input.