NPN CML ring oscillators for model verification and process monitoring

A set of NPN CML (Current Mode Logic) oscillators is designed in a 0.18um SiGe BiCMOS process, with the intention to provide model verification and process monitoring capabilities. The main design goals are that the oscillators need to be small and easy to test such that many of them can be placed in the scribe line and be measured by production PCM test equipment.