Design And Optimazation Of The Detection Circuit For A Novel High-linear Pressure Sensor Based On MEMS Fabrication

MEMS is an integrated technology which involves a variety of disciplines. MEMS capacitive sensor is an important part of it. Based on MEMS technology, a new high linear capacitive pressure sensor was developed, it can achieve good linearity theor-etically. However, design and improvement of readout circuit need improvement.Micro capacitive pressure sensor with good stability and sensitivity which plays an important role of detecting and changing non-electronic signals in micro-electro mechanical systems. When the detected non-electronic signal is reconverted to electronic signal, reading micro-power signals will become an important part. Therefore, the design of micro capacitive sensor interface circuit has a very important. This paper introduce five methods for the detection of micro-capacitance, and compare their advantages and disadvantages. We choose two parts as continuous readout voltage technology and capacity-frequency conversion circuit, to be used for the new high linear pressure sensor.Among the continuous voltage readout methods, micro capacitive readout circuit are designed by chopper stabilization technique so as to reduce circuit power consumption and improve noise performance. Each module circuits and circuit level simulation are verified, and based on Candence Spectre, the overall circuit verification accurate is to be aF level. Output voltage and capacitance maintain good linearity. Low power about 2.232mW is realized at 5V supply voltage. The offset voltage is only 0.22mV, with sensitivity of 0.58mV/aF. The power performance is better than the studies of other MEMS sensors.In the session of Capacitance-frequency conversion process, elimination of the difference frequency circuit common mode interference is proposed. Due to the frequency of the reference frequency signal and sensor output with the same process and temperature performance, the difference may be the greatest degree in two frequencies to eliminate common mode interference. By Candence simulation, the duty cycle of the square wave output reaches 50%. In the original six Schmitt trigger, based on the design of the improved version of the Schmitt trigger, the input port to reduce the parasitic capacitance of the threshold level while making adjustment easier. In the design of self-bias current source on the proposed reference current source three branches of negative feedback systems. Finally, in order to improve the sensitivity of the interface circuit, the design of a negative capacitance in parallel to the sensor capacitance sensitive and feasible through simulation. The final design sensitivity is to 25HZ/fF.In this paper, based on a high linearity silicon pressure sensor of our laboratory, chopper stabilization techniques and capacitive readout circuit design --- frequency conversion circuit are presented. Compared to similar studies, this work has high sensitivity. The research work in this thesis is not only to meet the performance MEMS sensors, but also provides a useful reference and value for the research and development of micro-capacitance detection circuit.