The claims define a processing circuit for processing input signals from a capacitive transducer structure. A current-to-voltage converter receives two input signals from the capacitive transducer structure, and outputs two output signals to gain stage circuits, and to a reference voltage generator. The gain stages generate from the output voltage signals a differential output signal. The reference voltage generates from the output signals a common mode output signal. The processing circuit generates a digital signal that corresponds to a quotient of the differential output signal and the common mode output signal.