Process variation compensated voltage controlled ring oscillator with Subtraction-based Voltage Controlled Current Source

In this work, we present a process variation compensated voltage-controlled ring oscillator (VCO) with the new Subtraction-based Voltage-Controlled Current Source (S-VCCS). The Subtraction-based Voltage-Controlled Current Source supplies the oscillator with a relatively stable current across process corners. A current starved ring oscillator structure with the proposed subtraction-based current source has been designed using the IBM 0.13um CMOS technology. Simulation results have shown that the proposed design using Subtraction-based Voltage Controlled Current Source (S-VCCS) can achieve approximately 50% reduction of the VCO´s process-induced frequency variation when compared to standard approach.