Design tradeoffs for improved V/sub CE(sat/) versus I/sub C/ of bipolar transistors under forced gain conditions

Based on the quasi-saturation analysis of bipolar transistors and using numerical simulation, it is shown in this paper that the quasi-saturation performance of transistors under forced gain conditions can be improved by increasing the base-Gummel number if the emitter diffusion is also simultaneously altered to keep the active region current gain h/sub FEO/ constant. It is further shown that for a given h/sub FEO/, if the ratio of h/sub FEO/ to the forced current gain /spl beta//sub f/ is below 10, the quasi-saturation performance of the transistors will be poor compared to those with h/sub FEO///spl beta//sub f//spl ges/10. Design curves obtained using numerical simulation are also presented to choose the quasi-saturation current limit of the transistors as a function of breakdown voltage and for different reach-through collector structures.<
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