Study of IEMP effects on IC operational amplifier circuits

Three typical operational amplifiers were irradiated by a plasma focus to study their IEMP responses with and without superposition of TREE responses. The 30-kJ plasma focus device produced photons primarily in the 8–100 keV range with pulse widths typically in the range of 10–15 nsec. Pulses of electrons were also deposited on the external leads of the op amps to determine the characteristic responses. These units were operated in circuits with closed-loop gains ranging from 5 to 100. During direct irradiation of the op amps, it was found that the IEMP responses (caused by photoemission within the housings) dominated the TREE responses provided that the RC time for the deposited charge to drainto ground was longer than a characteristic op arnp response time. The gas normally contained inside hermetically-sealed op amp units enhanced their IEMP responses. For most op amps, charge deposited on the input leads dominated the response, but some types were also sensitive to charge deposited on other external leads such as those controlling the offset.