Patent ID: 7288945

Claim:
A system comprising: a sensor electrode; a signal generator; a first op-amp comprising: a first inverting node coupled to the sensor electrode and a first non-inverting node coupled to the signal generator, where the sensor electrode is indirectly driven by the first op-amp and where the first op-amp provides a floating ground to the sensor electrode; a counter-electrode in proximity to the sensor electrode; a second op-amp comprising a second inverting node coupled to the counter-electrode and a second non-inverting node coupled to the signal generator, where the counter-electrode is indirectly driven by the second op-amp and where the second op-amp provides another floating ground to the counter-electrode; and a third op-amp comprising a third inverting node coupled to the output of the first op-amp and a third non-inverting node coupled to the output of the second op-amp, the third op-amp providing a differential signal between the sensor electrode and the counter-electrode.