Design of Readout Circuits Used for Micro-machined Capacitive Accelerometer

This paper describes a closed-loop micro-machined accelerometer implemented in a bulk-micromachining technology with integrated CMOS circuit. The operational principle of accelerometer is detailed. We establish a mathematical model of closed-loop system to compare the performance with the open accelerometer. Electrostatic force is served as a negative feedback in closed-loop operating mode to improve the bandwidth, linearity and dynamic range of micro-machined capacitive accelerometer. The noise source affected readout circuit is discussed to optimize circuit structure. The circuit is simulated using Hspice. The result of the circuit simulation shows good sensitivity and low power consumption. The sensor is designed to measure plusmn5g acceleration. Device sensitivity is larger than 15mV/g.