A Differential Output Switched Capacitor based Capacitive Sensor Interfacing Circuit

This paper presents a switched capacitor based capacitive sensor interfacing circuit, which can sense the change in capacitance from differential capacitive sensor and produces differential voltage output. The proposed circuit has the ability to reduce the errors like offset and low frequency noise introduced by the circuit components. The main advantage of this interfacing circuit is, it utilizes a single differential capacitive sensor and a single feedback network to provide differential output. The gain of the interfacing circuit is programmable through the feedback capacitor of the charge amplifier configuration. The interfacing circuit comprises of a fully differential operational amplifier, offset reduction scheme, buffer and low pass filter. The proposed circuit is designed and simulated using UMC 0.18-μm CMOS process technology. Both schematic and post-layout simulation results are presented.