Impact of TID-induced threshold deviations in analog building-blocks of operational amplifiers

This paper presents an investigation on the performance of analog building-blocks of two counterpart architectures of Operational Amplifiers (with PMOS and NMOS differential amplifier as input stage) under cumulative radiation effects. This investigation is performed through Spice simulations, by injecting typical radiation-induced shifts in the threshold voltage of the transistors for the considered technology, a 0.5 µm standard CMOS process. Transient and DC (Direct Current) analysis are performed in differential and inverter stages of a simple two-stage operational amplifier. The linearity and voltage swing of both amplifier stages are evaluated, as well as, the effects on the bias current and the output offset voltage. Simulation results show that the NMOS differential amplifier architecture may have an improved robustness in radiation environments, if compared to its PMOS counterpart, when considering the typical behavior of MOS transistors under radiation.