集成加速表设计

Integrated accelerometer design

以ＭＥＭＳ（微型机电系统）为基础的惯性仪表在汽车、计算机、导航等领域都将有广泛的应用。为了制作出低价格、小尺寸、中等精度的微型加速度计，有必要将接口电路和敏感元件集成在一个芯片上。本文介绍了一个体加工工艺的微机械敏感元件（包括一个差动电容结构）；分析了一种ＣＭＯＳ前置缓冲放大器和增量求和（Δ）原理的静电力反馈系统并且用计算机进行了仿真；同时对系统噪音进行了讨论。这个前置缓冲放大器可以达到２２ＭＨｚ的单位增益带宽和很小的运放输入电容。Δ反馈回路可以得到高精度和高线性度的数字输出。

The MEMS based intertial sensors have a wide range of applications in such fields as automotive, computer, and navigation. In order to obtain an MEMS accelerometer of low cost, small size and moderate accuracy and integrate the electronic interface circuits and the sensing element on a single chip is developed. The bulk micromechanical sensing element (including a differential capacitor) is presented. A CMOS front end buffer circuit and the summing increase Δ static electric force feedback system are analyzed and evaluated using computer simulations. The analysis of system noise is also discussed. The front end buffer can obtain a 22 MHz unity gain bandwidth and a very tiny amplifier input capacitance. The Δ feedback loop can get a digital output with high accuracy and linearity.