How to Design a Differential CMOS LC Oscillator

Abstract

CMOS oscillators that produce high frequencies with good spectral purity or low jitter are almost always realized as differential LC oscillators. This article gives a comprehensive treatment of this circuit for the practitioner who must make design choices and tradeoffs, and for the newcomer who wants to learn to do so. Phase noise is presented in the form of transfer functions from various noise sources, leading to compact, accurate expressions that guide design. Best practices for IC layout and operation at low voltages are given.