350 mV, 5 GHz Class-D Enhanced Swing Differential and Quadrature VCOs in 65 nm CMOS

A new enhanced swing class-D VCO which operates from a supply voltage as low as 300 mV is presented. The architectural advantages are described along with an analysis for the oscillation frequency. Prototype differential and quadrature variants of the proposed VCO have been implemented in a 65 nm RF CMOS process with a 5 GHz VCO oscillation frequency. At a 350 mV supply, the measured phase noise performance for the quadrature VCO with a 5% tuning range is -137.1 dBc/Hz at 3 MHz offset with a power dissipation of 2.1 mW from a 0.35 V supply. The highest resulting figure-of-merit (FoM) is 198.3 dBc/Hz.