A completely monolithic high-Q Q 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,

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... le 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 resonator. Although the high-Q Q Q of the micromechanical resonator does contribute to improved oscillator stability, its limited power-handling ability outweighs the Q Q Q benefits and prevents this oscillator from achieving the high short-term stability normally expected of high-Q Q Q oscillators.