Reliability Analysis of 0.5μm CMOS Operational Amplifiers under TID Effects
Keywords:CMOS Operational Amplifiers, Total Ionizing Dose, Radiation Effects, Inactivity Windows
Analog integrated circuits operating in radiation environments. In previous irradiation experiments performed on a switched-capacitor filter, implemented in a programmable analog array, it was observed a sudden recovery of the device performance during the irradiation, while increasing the accumulated dose. In some cases the considered performance parameters (such as the total harmonic distortion) may even be enhanced if compared to the pre-irradiation measurements, in specific accumulated dose intervals. This behavior is associated to partial inactivity windows in the internal components of the device. Spice simulations considering two complementary architectures of a simple CMOS Operational Amplifier (OpAmp) are performed, aiming to understand the origins of this effect. Results indicate that shifts on the operating point of the amplifier building blocks are responsible for the degradation and recovery of the OpAmp performance. Results also show that specific architectures, as well as, application constraints (such as the external feedback and the input signal amplitude and frequency) may result in different robustness levels related to the linear applications of the OpAmps in radiation environments.