A process compensated 3-GHz ring oscillator

In this paper, we present a high speed ring oscillator compensated for process, as well as temperature variation. No post-fabrication efforts or external clock reference is required to implement our process compensation scheme. By adding a novel control loop to the ring oscillator and leveraging a low process variation current source, we are able to reduce the typical variation from 10.2% to 2.7% for a 3-GHz three stage inverter chain ring oscillator. The compensation scheme developed in the paper is not limited to applications in ring oscillators, but can be used in all types of VCO designs.