Displacement and Transient Ionizing Synergistic Effects in μA741 Bipolar Amplifier

Displacement and transient ionizing synergistic effects in a custom
$\mu $
A741 bipolar amplifier were characterized experimentally under neutron pre-irradiation and subsequent pulsed X-ray irradiation. SPICE modeling method was also developed based on the displacement damage (DD) and transient photocurrent data of the transistors in the amplifier to explore the mechanism of the synergistic effects. The results indicate that with the increase of neutron fluence, the duration of transient ionizing response of the amplifier greatly shortens and the linear slope at the final recovery stage becomes slower evidently. The mechanism of the synergistic effects includes two aspects. Firstly, secondary photocurrents of the bipolar transistors significantly degrade after neutron pre-irradiation, leading to the reduction of voltage pull-down and pull-up capability of the transistors in the amplifier stage, and thus decreases the duration of transient response. Secondly, the slew rate of the amplifier obviously degrades due to DD, resulting in the reduction of the linear recovery slope at the final stage of the transient response.