An analog drive loop for a capacitive MEMS gyroscope

The linear model and the design of an analog drive loop for the drive (primary) resonator in a capacitive gyroscope are presented. Four different types of gain control topologies are compared and analyzed with both P- and PI-type controllers. The simple model proposed in the paper allows the small signal properties of the loop to be predicted. The theoretical models based on the small signal analysis are compared to the simulated and measured results. A proportional amplitude controller, together with the rest of the drive loop, is implemented using a high-voltage 0.35-mu m CMOS technology and a nominal supply of 3 V. Clock generation using a PLL and the drive loop signal as the reference are also discussed in the paper.