A dynamic range differential capacitive sensor interface circuit with noise shaping model of sigma-delta modulator

Most of the resistive type capacitive sensor interface circuits are used for specific application but they limits to measure or detect small changes, thus capacitive sensors are widely used in industry. In this paper we present an interface circuit for capacitance-to-voltage conversion for dynamic range that not only offers good signal-to-noise ratio but also it is used for dynamic range. So many capacitive sensor interface circuit has been proposed but they suffers to increase accuracy, to minimize post processing errors as well as low power application. This circuit uses sigma-delta conversion technique to reduce the interferences and it also improves noise performance. The sigma-delta modulator directly converts capacitance to digital codes. In this brief, we present an interface circuit topology with dynamic range of capacitance-to-voltage conversion for differential capacitive sensors. Differential capacitive sensing circuit employed to cancel or reduce the parasitic or stray capacitance of the sensor probes. Besides the interfacing circuit the third order continuous-time sigma-delta modulator and its noise shaping model is also presented.