Title :
Large-signal analysis of MOS varactors in CMOS -Gm LC VCOs
Author :
Bunch, Ryan Lee ; Raman, Sanjay
Author_Institution :
RF Micro Devices, Greensboro, NC, USA
Abstract :
MOS varactors are used extensively as tunable elements in the tank circuits of RF voltage-controlled oscillators (VCOs) based on submicrometer CMOS technologies. MOS varactor topologies include conventional D = S = B connected, inversion-mode (I-MOS), and accumulation-mode (A-MOS) structures. When incorporated into the VCO tank circuit, the large-signal swing of the VCO output oscillation modulates the varactor capacitance in time, resulting in a VCO tuning curve that deviates from the dc tuning curve of the particular varactor structure. This paper presents a detailed analysis of this large-signal effect. Simulated results are compared to measurements for an example 2.5-GHz complementary -Gm LC VCO using I-MOS varactors implemented in 0.35-μm CMOS technology.
Keywords :
CMOS analogue integrated circuits; UHF integrated circuits; UHF oscillators; circuit tuning; varactors; voltage-controlled oscillators; -Gm LC VCOs; 0.35 micron; 2.5 GHz; CMOS; I-MOS varactors; MOS varactors; RF voltage-controlled oscillators; accumulation-mode structures; inversion-mode structures; large-signal analysis; large-signal effect; large-signal swing; tank circuits; tunable elements; varactor capacitance; CMOS technology; Capacitance; Circuit optimization; Circuit topology; Integrated circuit technology; MOS devices; Radio frequency; Tunable circuits and devices; Varactors; Voltage-controlled oscillators;
Journal_Title :
Solid-State Circuits, IEEE Journal of
DOI :
10.1109/JSSC.2003.814416
