MEMS and sensors

In a parallel-plate electrostatic actuator, what is the phenomenon called in which, as the voltage rises, the movable electrode suddenly snaps to the fixed electrode once it passes a certain position?

  1. APiezoelectric effect
  2. BResonance
  3. CPull-in
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Answer: C. Pull-in

The electrostatic attraction grows sharply as the gap narrows, so at some point the spring's restoring force can no longer balance it. For parallel plates, this occurs after moving about one third of the initial gap; beyond that, the movable electrode snaps all the way. This is called pull-in and is considered when limiting travel and designing switches.

  • A. The piezoelectric effect is the generation of charge when force is applied to a piezoelectric material, or the reverse.
  • B. Resonance is vibration growing at a specific frequency.
  • C. Correct. The balance breaks and the electrode suddenly snaps in.
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  1. Which method is widely used to evaluate the bias stability (slow drift of the output) of MEMS gyroscopes?
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