Low-Voltage Electrostatic Actuation With Inherent Position Feedback

Electrostatic actuation in microelectromechanical systems (MEMS) often requires generation and control of high-voltage drive signals for sufficient force. Voltages in excess of a few volts require specialized circuit technologies and often cannot be implemented monolithically with other functions, such as precision sense amplifiers. This paper presents a circuit for enabling high-voltage actuation with low-voltage electronics by utilizing passive amplification provided by the Q factor of an electrical RLC resonator. The resonator is formed with the capacitive MEMS actuator connected in series to an inductor. Experimental results demonstrating voltage amplification by over an order of magnitude are presented. As a further benefit, the RLC circuit provides continuous position feedback in the form of position-dependent resonance frequency which is detected electronically. Inverse position dependence of the Q factor also extends stable range of parallel-plate actuators over that achieved with constant-voltage drive.