An extension of the charge control model for bipolar phototransistors

The charge control model (CCM) is extended to bipolar phototransistors, where a new effective lifetime is defined for the photocurrent of a phototransistor. The CCM is described for a phototransistor operated with its base terminal open. The assumptions implicitly made during the derivation of the model are discussed and a measurement scheme for the effective lifetime is presented. An example of the use of the extended CCM to predict the switching waveform of a phototransistor is presented. In this example, a simpler approach to using the CCM to predict the transistor's waveform is introduced.