NONLINEARITY AND HYSTERESIS OF RESONANT STRAIN-GAUGES

The nonlinearity and hysteresis effects of the electrostatically activ ated voltage-driven resonant microbridges have been studied theoretica lly and experimentally. It is shown that in order to avoid vibration i nstability and hysteresis to occur, the choices of the ac and de drivi ng voltages and of the quality factor of a resonator, with a given geo metry and choice of materials, are limited by a hysteresis criterion. The limiting conditions are also formulated as the hysteresis-free des ign rules, Expressions for the maximum allowable quality factor and ma ximum attainable figure of merit are given, Experimental results, as o btained from electrostatically driven vacuum-encapsulated low-pressure chemical-vapor deposition (LPCVD) polysilicon microbridges, are prese nted and show good agreement with the theory.