IEICE Electronics Express
Online ISSN : 1349-2543
ISSN-L : 1349-2543

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High performance differential Colpitts VCO with a linearized tuning range using a series resonator
Nam-Jin Oh
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JOURNAL FREE ACCESS Advance online publication

Article ID: 11.20140432

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Abstract

This paper proposes a novel low-phase noise Colpitts voltage-controlled oscillator (VCO) using a series LC network. For the series LC network, two capacitors are connected to each node of a parallel inductor-varactor tank (PLC). Each series connection node of the network is cross-coupled to the gates of switching transistors, and a large signal swing is achieved at each connection node. Also, the fixed biasing current sources of the differential Colpitts VCO are modified to operate as switched biasing current sources to lower the phase noise. Designed in 65 nm CMOS technology, the proposed VCO achieves a linearized tuning range from 3.73 to 3.97 GHz. The VCO consumes about 0.89 mW from a 0.4 V supply voltage, and achieves the phase noise of −123.3 dBc/Hz at 1 MHz offset. The calculated figure of merit of the VCO is about −195.5 dBc/Hz/mW.

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