High performance 1 V 2.4 GHz CMOS VCO

A low phase noise 2.4 GHz voltage controlled oscillator (VCO) with 1 V supply is presented. The VCO is based on the differential negative resistance oscillator with the tail current source replaced by an inductor. The inductor both improves the noise factor of the oscillator and enables maximum voltage swing over the tank. The amplitude limitation which is usually set by the tail current source is instead performed by an amplitude control loop adjusting the gate bias voltage. The oscillator measures a tuning range of 15%, a power consumption of 5.5 mW, and a phase noise of -136 dBc/Hz at 3 MHz offset from the carrier frequency for a 1 V supply.