An integrated CMOS micromechanical resonator high-Q oscillator

A completely monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator with the intent of achieving high stability. The operation and performance of m...

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Bibliographic Details
Published in:IEEE journal of solid-state circuits 1999-04, Vol.34 (4), p.440-455
Main Authors: Nguyen, C.T.-C., Howe, R.T.
Format: Article
Language:English
Subjects:
Circuit noise
Circuit stability
Circuits
CMOS
CMOS technology
Frequency
Integrated circuit technology
Mathematical models
Micromachining
Micromechanical devices
Oscillations
Oscillators
Resonance
Resonators
Semiconductor device modeling
Stability
Voltage
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Summary:A completely monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator with the intent of achieving high stability. The operation and performance of micromechanical resonators are modeled, with emphasis on circuit and noise modeling of multiport resonators. A series resonant oscillator design is discussed that utilizes a unique, gain-controllable transresistance sustaining amplifier. We show that in the absence of an automatic level control loop, the closed-loop, steady-state oscillation amplitude of this oscillator depends strongly upon the dc-bias voltage applied to the capacitively driven and sensed /spl mu/resonator. Although the high-Q of the micromechanical resonator does contribute to improved oscillator stability, its limited power-handling ability outweighs the Q benefits and prevents this oscillator from achieving the high short-term stability normally expected of high-Q oscillators.
ISSN:0018-9200
1558-173X
DOI:10.1109/4.753677