Degradation of the electrical characteristics of a bipolar transistor results from reverse-biasing the emitter-base junction and from irradiation with energetic electrons. The authors compare the degradation of advanced, self-aligned bipolar transistors by these two means. DC and AC characteristics of single devices are compared, showing that, apart from minor differences, the effects are similar. By cross-calibrating, it is therefore possible to use electron-beam irradiation to simulate emitter-base reverse bias stress in circuits in order to estimate its effect on circuit performance. Electron beam irradiation can be used as a diagnostic tool to determine the effect of stress on the performance of integrated circuits, in which the transistors are inaccessible to electrical test. The significance of electron beam damage on circuits has been demonstrated with a simple ECL (emitter coupled logic) case.