Resonant drive for stabilizing parallel-plate actuators beyond the pull-in point

In this paper, we present a circuit technique (resonant drive) that offers solutions for the three major challenges in electrostatic actuation and sense: (1) pull-in instability in parallel-plate actuators, (2) high voltage circuits for creating large electrostatic forces, (3) the need for extra circuitry and capacitor (in most cases) for position sensing. The key idea is a series LC tank formed by placing an inductor in series with the actuator capacitor and operating the circuit at its electrical resonance frequency by the help of an oscillator loop. Electronics operate at voltages significantly smaller (by the Q factor, 10-15, of the electrical tank) than the voltage needed for the electrostatic actuation of the MEMS device.