Compact voltage controlled ring oscillator with quadrature outputs

摘要

The compact voltage controlled ring oscillator includes two variable delay gates (VDGs). Each input port of one variable delay gate is connected to the output port of the other variable delay gate to form a feedback loop. A control interface receives an input voltage control signal (VCON), and generates a limited and buffered voltage control signal VX, which is provided to each of the VDGs to generate VDG bias currents which are limited and monotonic with VCON. Each VDG comprises a fixed bias differential transconductance gain stage (GM1), a variable bias differential transconductance hysteresis feedback stage (GM2), and a variable bias voltage follower stage. The combination of delay control from variable hysteresis and variable voltage follower output resistance provides a compact, low power ring oscillator VCO, with over an octave of tuning range.