The Design and Analysis of Dual-Delay-Path Ring Oscillators

A dual-operation-mode ring oscillator that employs dual-delay paths is presented. The two operation modes, referred to as the differential and common modes, have different output waveform characteristics and oscillation frequencies. A nonlinear model for the dual-delay-path ring oscillator and the analysis of the stability of each operation mode are proposed to confirm both simulation and measurement results. Furthermore, a method for operation-mode selection is presented. The differential four-stage dual-delay-path ring oscillator is fabricated in a 0.18-μm CMOS technology. Measurements show that the tuning ranges are from 1.77 to 1.92 GHz and from 1.01 to 1.055 GHz for differential- and common-mode operations, respectively.