This paper appears in: Solid-State Circuits, IEEE Journal of
Publication Date: Nov. 2009
Volume: 44,
Issue: 11
On page(s): 3079-3091
ISSN: 0018-9200
Digital Object Identifier: 10.1109/JSSC.2009.2031519
Current Version Published: 2009-11-03
Abstract This paper presents a ${g} _{ m}$-boosted differential gate-to-source feedback Colpitts (GS-Colpitts) CMOS voltage-controlled oscillator (VCO) that consumes a lower oscillation start-up current. The proposed architecture allows a wider range of saturation mode operation for the switching transistors, which helps suppress AM-to-FM conversion by these transistors. In addition, the phase noise contribution of the flicker noise in the switching transistor is reduced through the capacitor feedback network of the Colpitts oscillator. As a result, the proposed topology can achieve better phase noise performance and a higher figure of merit (FOM) compared to a conventional NMOS-only cross-coupled VCO. The proposed VCO is implemented in a 0.18-$mu{hbox {m}}$ CMOS for 1.78 to 1.93 GHz operation. At 1.86 GHz, the measurements show phase noise of $-$105 and $-hbox{128~dBc/Hz}$ (corresponding to ${rm FOM}= 191.2$) at offsets of 100 kHz and 1 MHz, respectively, while dissipating 1.8 mA from a 0.9-V supply.
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