ZHANG Hui(张慧)1, HE Chang-de(何常德)1,2, MIAO Jing(苗静)1, LIAN De-qin(廉德钦)1,2, ZHANG Wen-dong(张文栋)1,2, XUE Chen-yang(薛晨阳)1,2
(1. Key Laboratory of Instrumentation Science & Dynamic Measurement (North University of China), Ministry of Education, Taiyuan 030051, China;2. Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China)
Abstract： With the development of micro-electro-mechanical system (MEMS) technology, the MEMS-based capacitive sensor has been widely applied in the field of electron components. However, the capacitance of the micromachined sensor is so small that the detection of the smaller value change of the capacitance is a great challenge. Based on the principle of charging and discharging of the capacitor, a kind of pulse width modulated differential circuit is introduced in this paper. For subsequent amplification, a modified amplifier is presented. The differential circuit converts the weak capacitance change to the change of the pulse width of the output voltage, and the linear relationship can be obtained. And the modified amplifier implements the processes of amplification and filtering synchronously, and a large DC output voltage can be obtained by the low-pass filter. The designed circuits have advantages as simplified circuit, high voltage stability, perfect linearity and resolution. Besides, it is feasible to be integrated with the sensor to largely reduce the transmission error and interference.
Key words：capacitive detection; capacitance transform; width modulation differential circuit; modified amplifier
CLD number： TP212.1 Document code： A
Article ID： 1674-8042(2013)02-0111-05 doi： 10.3969/j.issn.1674-8042.2013.02.002
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