Torque multiplication and stable range tradeoff in parallel plate angular electrostatic actuators with fixed DC bias

The nonlinear torque-voltage characteristics in two-terminal electrostatic actuators can be utilized to magnify the torque generated by a drive voltage applied to one electrode if a fixed dc bias is applied to the other. The resulting torque is enhanced by torque gain factor G_τ>1, and the drive voltage is effectively multiplied by voltage gain factor G_V>1 compared to that of an actuator with no dc bias. These gain factors are generated at the expense of a reduced stable range. In this paper, we study and determine experimentally the tradeoff between torque and voltage gains versus stable range for one-dimensional (1-D), three-terminal, parallel-plate angular electrostatic actuators under dc bias. Simple approximate analytical relations are derived for voltage and torque gain as functions of applied dc bias voltage. We demonstrate that for voltage gains of 2-4, the angular range is marginally reduced. [1361].