Patent ID: 6925325

Claim:
An apparatus for sensing signals relative to a voltage at a ground node, the apparatus comprising: first, second, third, fourth, control, and ground nodes; a first series impedance providing a first gain between the first and third nodes; a first shunt impedance between the third and ground nodes; a second series impedance providing a second gain between the second and fourth nodes; a second shunt impedance between the fourth and control nodes; a differential amplifier having inputs coupled to the third and fourth nodes and an output representative of a differential signal; a common mode amplifier having inputs coupled to the third and fourth nodes and an output representative of a common mode signal; and a control circuit, coupled to the differential amplifier output to receive the differential signal and coupled to the common mode amplifier to receive the common mode signal, the control circuit also coupled to the control node for providing a control signal such that a first gain between the first and third nodes approximately matches a second gain between the second and fourth nodes.