In this letter, a class-C architecture for an oscillator employing film bulk acoustic resonator (FBAR) is presented to improve the phase noise significantly in 1/f 3 region. The advantages offers by class-C operation are exploited in order to reduce the noise contributed by the current-source transistor in cross-coupled topology. An adaptive biasing circuit is used in order to ensure the oscillation start-up. The post-layout simulation incorporating all parasitic and representing FBAR by

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... d Butterworth Van Dyke (MBVD) model illustrates the phase noise improvement by 17 dBc/Hz at 100 kHz offset of a 1.9 GHz carrier compared to the FBAR based cross-coupled topology presented by the authors [1].