A high swing low power CMOS differential voltage-controlled ring oscillator

This paper presents a two-stage CMOS differential voltage-controlled ring oscillator (VCO). The VCO is intended to operate as a frequency synthesizer in a PLL to generate local oscillator frequency (LO) for an acquisition system, providing in-phase/Q-phase outputs. This workproposes a differential VCO design that has a wide operating frequency tuning range with low power consumption, better phase-noise performance and good linearity between the ftequency and control voltage. Simulation results verify the theoretical development and address the layout design. The circuit was designed and simulated in 0.18 mu m IBM CMOS technology.