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A new enhanced swing differential Colpitts VCO architecture enables oscillations to go beyond both the supply voltage and ground making it suitable for low voltage operation. Analysis for the oscillation frequency, differential- and common-mode oscillations, amplitude of oscillation, and start-up condition provides insight into oscillator operation and design considerations. Operating at 4.9 GHz, the VCO consumes from 1.9 mW to 3 mW for supply voltages of 400 mV and 500 mV, respectively. The 130 nm CMOS VCO's measured phase noise ranges from -132.6 to -136.2 dBc/Hz at a 3 MHz offset frequency.
Date of Publication: Aug. 2011