An Ultra-Low Noise Capacitive Readout Circuit for Gyroscopes

Based on a continuous time voltage sensing, this paper presents an ultra-low noise capacitive readout circuit for capacitive gyroscopes which has a capacitive signal varying from 0 to 0.3 pF and its frequency is ranged from 10 to 20 kHz. The readout circuit is implemented by a charge sensitive amplifier (CSA) with both input and output common feedback circuit. The signal modulation technique controlled by 1 MHz carrier clock is adopted to shift low-frequency capacitive signal to high frequency and significantly release design requirement of the CSA. The proposed capacitive readout circuit is implemented based on 0.18-μm CMOS process, and the simulation results show that the designed readout circuit at a fixed 3.3 V supply voltage and common-mode voltage of 1.5 V achieves a resolution as low as 0.03 aF/sqrt Hz@10 kHz.