A Wide Range CMOS VCO for PLL Applications

This paper describes a six phase differential wide range CMOS voltage controlled oscillator (VCO) designed for PLL applications. The VCO bias scheme includes a rail to rail operational trans-conductance amplifier (OTA), which enhances the useful control voltage range. A novel temperature compensation scheme is also proposed to minimize the temperature dependence of oscillation frequency. External trim bits are used to reduce frequency variation across process corners. Simulation results from a 65nm LP CMOS technology with supply voltage of 1.2V are also discussed. A wide frequency range from 1GHz to 4GHz is achieved.