A 3-V 4-GHz nMOS voltage-controlled oscillator with integrated resonator

A 4-GHz fully-monolithic nMOS voltage-controlled oscillator circuit implemented in a 0.5-μm BiCMOS technology is presented. The tuning range is 9% with an on-chip varactortuned resonator and a control voltage of 0-3 V. The measured phase noise is -85 dBc/Hz at 100 kHz and -106 dBc/Hz at 1 MHz offset. The circuit draws 8 mA from a 3 V supply including the reference branch bias current. Even with the supply voltage and the variation in control voltage reduced to 2.3 V, the VCO has a tuning range of 8%.