Limitations of a relaxation oscillator in capacitance measurements

Abstract

Oscillation periods of a relaxation oscillator consisting of an op-amp-based integrator and a comparator are measured over a wide range of RC integration constants, and the results are compared with theoretical values derived in terms of the finite gain-bandwidth (GB) product and the slew rate of an op-amp and the response delay of a comparator. The comparison validates the theoretical derivation which gives the design criteria of a relaxation oscillator for capacitance measurements and sensor signal processing.