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为了改善微机电系统(MEMS)电容式加速度计的噪声特性,提出了一种基于开关电容的低噪声闭环接口电路。该电路采用电荷积分器作为前级预放大装置,对寄生电容不敏感,而且具有非常低的噪声。采用相关双采样(CDS)技术消除了1/f噪声和运算放大器失调电压的影响。同时,为了改善系统的动态响应特性,反馈部分采用积分电路,提高了系统阻尼比和响应速度。利用电荷泻放通道实现了自检测功能。采用0.5μm CMOS工艺完成了版图设计,仿真结果表明,系统灵敏度为0.115V/g,非线性度<0.12 %,可检测的最小加速度为20μg,自检测输出与自检测电压成正比。
In order to improve the noise characteristics of MEMS capacitive accelerometer, a low noise closed loop interface circuit based on switched capacitor is proposed. The circuit uses a charge integrator as a pre-amplifier, which is insensitive to parasitic capacitance and has very low noise. The use of correlated double sampling (CDS) eliminates 1 / f noise and op amp offset voltage. At the same time, in order to improve the dynamic response of the system, the feedback part adopts the integral circuit to improve the system damping ratio and response speed. The use of charge-discharge channel to achieve a self-test function. The layout design was completed by 0.5μm CMOS technology. The simulation results show that the sensitivity of the system is 0.115V / g, the nonlinearity is less than 0.12%, the minimum detectable acceleration is 20μg, and the self-test output is proportional to the self-test voltage.