EMITTER SERIES RESISTANCE FROM OPEN-COLLECTOR MEASUREMENTS INFLUENCE OF THE COLLECTOR REGION AND THE PARASITIC PNP TRANSISTOR

The open-collector method for determination of the emitter series resi stance in integrated bipolar transistors is analyzed. Existing models do not provide the accuracy required for a correct determination of th e emitter series resistance. In order to accurately describe the satur ation voltage, a set of model equations is derived that provides a mor e accurate description of the epitaxial collector region. The measured V-CE(I-E) characteristic is found to depend on the properties of the collector region as well as the parasitic substrate transistor. Using the model developed, a consistent description of measurement results f or different bias conditions of the collector-substrate junction is po ssible. With this new understanding of the open-collector method, an i mproved procedure to extract the emitter resistance from measurement d ata is developed, and results of the method applied to integrated bipo lar transistors are presented.