Ferroelectric Negative Capacitance Inspired Driver Circuits for Electrostatic MEMS Actuators

Abstract

Electrostatic MEMS actuators require high operating voltages. It has been predicted that a ferroelectric negative capacitance connected in series with a MEMS actuator, forming a hybrid actuator, can reduce its operating voltage. We propose a driver circuit that mimics the behaviour of such hybrid actuators. Electrostatic actuators also suffer from pull-in instability, wherein the movable electrode snaps down to hit the bottom electrode beyond a certain applied voltage, called the pull-in voltage. Pull-in instability prohibits the use of entire air-gap for stable operation. We modify the proposed driver circuit to eliminate pull-in, resulting in full-gap travel. Using our topology, we illustrate both non-linear and linear quasi-static response for pull-in free operation. The results obtained using the numerical and circuit simulations and analytical predictions are in good agreement with each other. Thus, the proposed driver circuits can aid in the design of pull-in free electrostatic MEMS actuators.