Voltage Controlled Oscillator for Small-Signal Capacitance Sensing

Abstract

Voltage Controlled Oscillator (VCo) for gas measurement with a MOS capacitor sensor is designed starting from an Armstrong topology and a prototype is tested. The VCO ensures a small signal level across the sensor (< 100mV), necessary for precise measurement. A method in which the frequency of the oscillator is maintained constant by adjusting the sensor bias is proposed.