  We find in experiments a linear dependence of ionization irradiation-induced
degradations on pre-irradiation values of the input bias current in bipolar
devices with simple input stages. The dependence is found to generally exist in
all studied cases of different device types and different irradiation
conditions. A unique behavior of the energy distribution of the interface
states ($D_{it}$) under irradiation is suggested as the origin of the observed
phenomenon: the generation of interface traps through the depassivation of Si-H
bonds located near the pre-irradiation interface traps displays a $D_{it}$ as
an enlarge of the initial $D_{it}$ and results in the general linear
dependence. A more accurate damage prediction method by using the
pre-irradiation values is proposed based on the observed phenomenon.
