Modification of the TRAC Ebers-Moll Model for Improved High Frequency and Collector Storage Time Predictions

The present TRAC Ebers-Moll model is modified in order to obtain an improved high frequency prediction. This is achieved by means of a three lump Linvill model to account for diffusion transport of minority carriers in the base region of a bipolar transistor. The modified Ebers-Moll model obtained in this manner yields two pole representations for the transport factors in the frequency domain. The two pole representation for hfe is shown to give reasonable fit both in amplitude and phase with experimental data obtained from a low frequency bipolar transistor, while the phase correlation obtained with the single pole representation of the present TRAC Ebers-Moll model is unsatisfactory, especially, at high frequencies. The present TRAC Ebers-Moll model was also modified so as to obtain an improvement in collector storage and recovery time prediction. This was accomplished by the introduction of two Linvill lumps in the collector region to account for minority carrier storage and transport. The observed experimental collector-base diode turn-off transient response for the same low frequency bipolar transistor was found to be in agreement with the prediction of the modified model. Finally, the paper is concluded with a discussion of a modified model to account for both the high frequency response, as well as, collector storage and recovery time effects.