TRANSIENT BASE DYNAMICS OF BIPOLAR-TRANSISTORS IN HIGH INJECTION

The transient behavior of a bipolar transistor in high level injection is analyzed both through simulations and an analytic model based on t he quasi-neutral base approximation, It is found that, unlike the situ ation for low injection, transient operation can be influenced by the base majority carrier mobility and by the characteristics of the extri nsic base, While the quasineutrality approximation frequently remains valid, cases are presented in which it fails, In these cases, the tran sient conditions cause at least some small region of the normally quas i-neutral base to develop a space charge, The reclaimable fraction of the stored base charge is determined and discussed.