A CMOS Colpitts Voltage-Controlled Oscillator with Bias-Free pMOSFET Tails

A new fully integrated CMOS voltage-controlled oscillator (VCO) is presented. The VCO is composed of cross-coupled Colpitts negative resistance cell in shunt with a parallel-turned LC resonator and was implemented in 90 nm CMOS technology. The negative resistance cell uses bias-free pMOS tail for low-phase noise design. With the supply voltage of 1.15 V, the VCO is tunable from 18 GHz to 20.25 GHz while the tuning voltage varies from 0V to 1.4 V. The phase noise of the VCO operating at 18 GHz is -117.34 dBc/Hz at 1 MHz offset, while the VCO draws 7.07 mA and uses 8.13 mW consumption.