Noise suppression of MEMS readout near pull-in

We show that electromechanical feedback in MEMS sensors can be used to eliminate the noise of the readout electronics near the pull-in point, at which the force-to-displacement gain of the system becomes infinite. Displacement bias through electrical feedback instead of voltage bias allows stable operation up to and above the pull-in point. Experimentally, the electronics contribution to system resolution was suppressed by an order of magnitude, reaching the intrinsic resolution of the MEMS microphone. The technique allows the use of standard integrated electronics with noise-critical MEMS sensors, such as microphones, pressure sensors and accelerometers.