Design of a Wide-Band Voltage-Controlled Ring Oscillator Implemented in 180 nm CMOS Technology

The design of a wide-band voltage-controlled oscillator (VCO) modified as a VCO with programmable tail currents is introduced herein. The VCO is implemented by using CMOS current-mode logic stages, which are based on differential pairs that are connected in a ring topology. SPICE simulation results show that the VCO operates within the frequency ranges of 2.65–5.65 GHz, and when it is modified, the VCO with programmable tail currents operates between 1.38 GHz and 4.72 GHz. The design of the CMOS differential stage is detailed along with the symbolic approximation of its dominant pole, which is varied to increase the frequency response in order to achieve a higher oscillation frequency when implementing the ring oscillator structure. The layout of the VCO is described and pre- and post-layout simulations are provided, which are in good agreement using CMOS technology of 180 nm. Finally, process, voltage and temperature variations are performed to guarantee robustness of the designed CMOS ring oscillator.