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This paper describes an interface circuit design for monolithic CMOS-MEMS gyroscopes, based on a novel differential difference amplifier (DDA) with high gain, low temperature and process dependence, low noise, and low power consumption. The DDA achieves a 4 fF equivalent transcapacitance with a 0.01%/°C temperature variation. The DDA-based interface circuit has been integrated with a z-axis gyroscope on a foundry CMOS chip. A 4.5 zF/√Hz input-referred noise is achieved at 2 kHz, with a total power consumption of 4.25 mW. The gyroscope is fabricated with a post-CMOS bulk micromachining process and the device achieves a sensitivity of 1.2 mV/°/s and a noise floor 0.05 °/s/√Hz.