An Uncalibrated Wide-Range Single-Supply Integrable Front-End for Resistance and Capacitance Estimation

In this work a CMOS fully-integrable circuit for wide-range resistance estimation is presented. The proposed circuit, thanks to the adopted resistance-to-time conversion, is able to operate over more than six decades of resistance values (from 100 kOmega to more than 100 GOmega) being suitable for resistive gas sensors. In addition, the estimation of a parallel capacitive component (in the order of few pF), that could be the sensor parasitic capacitance, is possible. The circuit is designed to operate with a single-supply voltage (3.3 V) to simplify the integration in a standard CMOS technology together with the digital components needed to the time measurement. Experimental results, obtained using a discrete-component prototype, show high linearity and reduced percentage error between measured and theoretical results.