Current reused LC VCOs

This paper presents current reused voltage controlled oscillator (VCO) topologies by stacking switching transistors in series like a cascode. The VCOs can operate with only half the amount of dc current compared to those of the conventional VCO topologies. Fabricated in 0.18-μm CMOS process, a differential VCO operates in a 2.1-GHz band with a phase noise of -110dBc/Hz at 1-MHz offset, and a quadrature VCO operates in a 3.1-GHz band with a phase noise of -102dBc/Hz at 1-MHz offset. The proposed topologies can be adopted for low-power applications.