Groups of a typical operational amplifier-mu A741 were irradiated in a cobalt unit, each group accumulating a different total ionizing dose (TID). The results showed that the TID caused power consumption current and slew rate (SR) to degenerate in ultra-linearity, owing to a severe reduction in the current gain of the internal LPNP transistors. Pulsed X-ray irradiation experiments were carried out on the mu A741 groups with different values, and the results revealed that the impact on the response to the pulsed X-ray irradiation was greater when the devices absorbed more TID. The mechanism for this is explained on the basis of the circuit construction of the mu A741; the sensitive parameters of the circuit were obtained via simulation on SPICE. The simulation results additionally showed that if the sensitive parameters were optimized, the duration of interruption caused by the pulsed X-ray irradiation would be reduced significantly. In addition, several proposals are provided for hardening the devices.