A Compact Parasitic-Insensitive Dual-Frequency ∆Σ Modulated CMOS Capacitive Sensor

Abstract

We present a simple, high-sensitivity, array-based capacitive sensor for biological applications. The circuit can accurately sense ungrounded coupling capacitances, while strongly attenuating the effect of unwanted parasitics. It can also perform capacitance-voltage profiling of nonlinear biological capacitances at very low voltages. We implement a dual input frequency ∆Σ modulator to perform improved noise filtering and an increased dynamic range. We verify the circuit implemented in a 0.35μm CMOS technology by simulating for different values of parasitic capacitances, process corners and varying test voltages across capacitors.

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