Effective base resistance of bipolar transistors

Two formulations, one appropriate for dc analysis and the other for low-frequency ac analysis, are developed to calculate effective lumped base resistance of bipolar junction transistors. These formulations are defined in terms of terminal characteristics, and are more appropriate for device behavior in circuit modeling applications than those formulations currently in the literature. This is most apparent at high current levels, where appreciable current crowding is present and all of the models under consideration give markedly different results. The present calculations are made for a discrete transistor of single base-stripe geometry, but the results are applicable to integrated-circuit transistors and can be readily extended to other geometries.