P2.9.5 A Novel OA-Based Oscillating Circuit for Uncalibrated Capacitive and Resistive Sensor Interfacing Applications

Andrea De Marcellis, Giuseppe Ferri & Paolo Mantenuto
In this paper, we propose a novel square-wave oscillator, based on Operational Amplifier (OA), making an impedance-to-period (Z-T) conversion that, instead of a voltage integration typically performed by other solution presented in the literature, is based on a voltage differentiation. This circuit is suitable as first analog front-end for both capacitive (e.g., for relative humidity) and resistive (e.g., for gas) sensors, working also for wide-range variations (e.g., about 6 capacitive variation decades). Circuit sensitivity can...