A low-power capacitance measurement circuit with high resolution and high degree of linearity

This paper has presented a low-power capacitance read-out circuit which could be used for biomedical sensor applications. The differential structure of the system eliminates even order distortion. The entire system manifests two current sense amplifiers, two diode rectifiers and one instrumentation amplifier. The circuit has been realized using TSMC 0.35 mum bulk CMOS process. The circuit operates with a 3 V power supply and consumes 5.384 mW of power. Simulation results show that the circuit has a sensitivity of 1.32 mV for 1 fF capacitance change. Measurement results for different capacitance variations demonstrate a change of 10.8 mV for 8.8 fF variation.