Influence of Collector Recombination Lifetime on the Current Gain and Storage Time of High-Voltage Power Transitors
SourceTwo new charge control models are described that account for the effect of collector recombination on transistor current gain, hFE, and storage time, tS. For hFE it is shown that the collector lifetime, τ, is usually large enough that collector recombination can be ignored. As τ is decreased, this assumption is no longer valid, and hFE eventually becomes proportional to τ.
The lifetime is also important in determining tS at low collector currents, where tS is approximately proportional to τ. The resulting trade-off between hFE and tS is determined quantitatively for a particular example by using the proposed models.
Additional data are given that show that both models agree well with experimental measurements. The comparison is made using measured open-circuit-decay lifetimes in the theoretical calculations.