Continuous-time interface for a micromachined capacitive accelerometer with NEA of 4 μg and bandwidth of 300 Hz

A continuous-time accelerometer interface is feasible when a high dynamic range together with a wide signal band is required. In this paper the implementation of a continuous-time force-feedback loop for a capacitive sensor element with a full-scale signal of ±1.5±1.5 g is presented. The interface is measured to attain a noise equivalent acceleration (NEA) density of 500 ng/Hz at 30 Hz for the on-chip digitized output and 300 ng/Hz at 30 Hz for the analog output using a capacitive half-bridge sensor element with a single pair of electrodes. The essential circuit structures of the closed-loop sensor will be presented and analyzed in detail.