Large electrostatic forces on a micromechanical capacitor plate can be obtained if the capacitor is tuned by using an inductor. Such an LC circuit can be used to control the position of a micromechanical capacitor plate over a large dynamic range. The pull-in phenomenon of capacitor plates does not occur because the LC drive is intrinsically stable. The LC drive can be implemented either by sweeping the frequency or the amplitude of the driving AC voltage. In both cases relatively good linearity can be obtained. It is found that the LC drive can tolerate large parasitic capacitances. Measurements done on a dual capacitive acceleration sensor verify the calculated results. A drive AC voltage rms amplitude of 10% of the DC pull-in voltage deflected the moving plate by about 60% of the nominal gap, limited only by a mechanical stopper.
- Electrostatic actuation
- Micromechanical capacitor