Circuit Applications of Transient Annealing

A method is presented for predicting transistor annealing factors, in continuously ON devices, from a simple electrical measurement on a device. A nomograph has been derived from experimental data which relates annealing factors at any time after exposure to the electron density in the base-emitter space-charge region. The electron density in this region can be obtained by a single measurement of VEE, at the transistor operating current of interest. The effects of transient annealing are investigated for two typical circuit situations (power-inverter circuits and logic circuits) where devices may be OFF during irradiation and subsequently required to turn ON. The Darlington circuits utilized in typical power-inverters prolong the annealing, if OFF when exposed. The propagation delay of a NAND gate series pair is increased considerably at early times after a neutron exposure. This additional delay can result in reduced pulse width or lost pulses.