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M. Kucera, F. Hofbauer, T. Manzaneque, V Ruiz-Díez, A. Bittner, J.L. Sànchez-Rojas, U. Schmid:
"Quality Factor Enhancement for Resonant MEMS Applying an Analogue Feedback Circuit Driven by a Lock-in Amplifier";
Vortrag: SPIE Microtechnologies 2013, Grenoble, France; 24.04.2013 - 26.04.2013; in: "Proceedings of SPIE", 8763 (2013), ISSN: 0277-786x.

In this study, an analogue Q-control circuit is presented, based on a digital feedback loop. In this approach, a selfactuated
and self-sensing piezoelectric microstructure is used in combination with a lock-in amplifier to extract the Qcontrol
feedback signal amplitude which is proportional to the piezoelectric current. In the next step, the DC-value
supported by the lock-in amplifier is multiplied with a sine signal on a custom-designed analogue circuit board
containing an analogue amplifier IC. This generated analogue feedback signal allows to drive a complete analogue
feedback loop enabling faster response of the Q-control and further faster measurements can be performed. Using this Qfactor
enhancement technique, the Q-factor was increased from 397 to about 5357 in air without driving the used Qcontrol
approach to its limits. These promising results will push further activities in measuring the viscosity of liquids in
the future.

MEMS, piezoelectric AlN, Quality factor enhancement, Q-control, analogue feedback, self-sensing