Previous prediction methods1 are extended by analysis of new experimental data. Improved engineering techniques are developed for predicting equilibrium primary photocurrents from transistor electrical parameters. For silicon low power planar and mesa transistors, Â¿ICBO is related to high base current electrical storage time by a simple prediction equation. A radiation storage time parameter is defined and theoretical and empirical equations for radiation storage time are developed. A radiation storage time transistor model and nomograph are presented to simplify pulsed radiation response predictions by circuit designers. The techniques are unique in predicting radiation responses entirely from measured preirradiation transistor electrical parameters.