Abstract
An intuitive yet suf ficiently accurate formulation of the phase noise of various commonly used oscillators, including most types of class-B (standar d, AC-coupled and with tail filter) and class-C, is derived and used to compare their fundamental lim- itations. A noise factor that represents the difference between the maximum achievable Figure of Merit and the actual one is derived for all topologies considered. Measurements on a dedicated chip prototype that integrates two high performance topologies allow to verify, in an unbiased way, the accuracy of the predictions. A very good agreement between the mo del and both simulation and measurement is obtained.