Frequency control schemes for single-ended ring oscillators

An analysis of frequency control techniques for inverter based ring oscillators is presented. The aim of this study is to aid the circuit designer in architecture selection appropriate for a specific application. A brief discussion on ring oscillators is presented followed by an overview of the various control schemes. The circuits are realized in a 40 nm CMOS technology and simulated using Spectre. Based on simulation results the different control schemes are characterized in terms power consumption, tuning range and noise performance so as to guide the designer about the control scheme selection.