Compact modeling of the influence of emitter stored charge on the high frequency small signal AC response of bipolar transistors using quasi-static parameters

A model involving only quasi-static parameters is proposed which is capable of modeling the influence of high frequency nonquasi-static stored charge distributions in the neutral emitter region on the small signal high frequency ac response of bipolar transistors. Quasi-static ac model parameters are completely determined from static charge distributions for arbitrary impurity profiles, thereby enabling high frequency behavior to be accurately deduced for realistic device structures without the need for high frequency numerical simulation or measurement. The proposed model provides quantitative information regarding the transition from quasi-static to nonquasi-static behavior of emitter stored charges. An existing equivalent circuit representation that accurately models the influence of the stored base charge, and which is suitable for SPICE simulations, is modified to include the impact of quasi-static charge distributions in the emitter region.