Relaxation of operational amplifier parameters after pulsed electron beam irradiation

Abstract

The relaxation of operational amplifier parameters (offset voltage and differential gain) with time after pulsed electron beam irradiation has been studied as a function of total dose and amplifier type. Four types of operational amplifiers were studied viz., general purpose bipolar input (μA 741), super-beta transistor input (LM 308), JFET input (LF 356) and MOSFET input (CA 3140) from different vendors. The experiments were carried out mainly using 500 ns pulses from a Linear Accelerator. The study, the first of its kind, shows that while the electrical transient at the output of the operational amplifier recovers in a few milliseconds, relaxation of parameters can take several to several tens of seconds. This relaxation is attributed to the build up and/or anneal of damage in the oxide or at the interface of the internal transistor structures. The change and relaxation of parameters depend on operational amplifier type and total dose, and can have significant effects in certain application domains as illustrated by the response of a thermocouple amplifier after pulsed irradiation.