Large Range Accelerometer Readout Circuit Design And Research

The rapid development of integrated circuits and MEMS technologies promoted the researches and applications of silicon micro accelerometer. This thesis gives a readout circuit for large accelerator measuring, In view of the fact that the present domestic research achievements are small measuring range. Using the principle of electrostatic force feedback can greatly enhanced the reading circuit measuring range, and it can be integrated with the accelerometer for the circuit design is based on typical CMOS process.The principle of the readout circuit is analyzed first, close-loop mode is chosen after comparing with the open-loop mode. The measuring range has been inferred under this mode.Then the modules of the readout circuit have been designed, following the analysis of the former chapters. Large size PMOS transistors have been used for input pair in the preamplifier OP, to reduce the 1/f noise, and the filers are realized by switching-capacitor method. And the OP of the output stage is a two-stage amplifier, which is complemented by Miller capacitor and nulling resistor to get good performance in frequency domain.Next circuit noise mechanism of the readout circuit has been analyzed. Noise reducing methods has been used according to the noise principles. Modulation and demodulation can reduce low frequency noise markedly, and Modulation and demodulation has been analyzed in frequency domain.Finally the readout circuit has been simulated using Cadence based on the SMIC 0.35μm 5V process. According to the simulation results the performances of all modules have met the requirements of the system. The open-loop gains of the Ops of the filters, preamplifier stage, demodulation circuit, output stage are larger than 66 dB, and PM is larger than 45°. For the largest input signal 70g, the output voltage is 3.92V. Linearity is smaller than 1%.So the readout circuit can measure 70g accelerometer within 1% linearity using close-loop electrostatic force feedback. And the research result is very meaningful for spaceflight and aviation.