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A low-power interface for readout and motion-control of a MEMS capacitive sensor is presented. The interface consists of a hybrid third-order sigma-delta modulator. The interface enhances the linearity and stability of the sensor by applying force feedback through bias voltage modulation. The modulator employs a hybrid, continuous + discrete-time topology, to reduce power consumption by avoiding a separate pre-amplifier for the sensor. Power consumption in the modulator is further reduced by an op-amp sharing scheme. The interface is designed in 0.35 um CMOS technology and is simulated in Cadence-Spectre. Simulation results are shown for a MEMS capacitive microphone.