Abstract:

In order to satisfy the requirement of capacitive weak signal sensing in the general micro-electro-mechanical-system(MEMS) device or gauge, a capacitive sensing circuit with ring diode demodulation is designed and experimentally verified. This circuit is mainly composed of C/V transformation, band pass filter (BPF), ring-diode demodulation, differential amplification and so on. From the Pspice simulation and experimental results, the sensitivity of this circuit can reach as high as 3.12V/pF, which corresponds to displacement measurement on the nanometer level for a general MEMS device. Due to its features such as small volume, low power consumption as well as easiness in integral, this circuit has favorable and practical value for MEMS devices such as accelerometer, gyro and pressure sensors.

Key words: Microelectromechanical system (MEMS), capacitive sensing of microdisplacement, diode demodulation, sensitivity