Total dose effect on optocouplers subjected to different dose rate irradiation

60Co irradiation on optocouplers is examined at dose rate of 0.01, 0.1, 1.0 and 50 rad/s. The experimental results show that current transfer ratio decreases after exposure and the amplitude of degradation at a given total dose depends on the dose rate, namely more degradation with lower dose rate. The I-V characteristics of LED, gain and primary photocurrent of phototransistor, and transmission loss in optical coupling medium are tested and analyzed, which lead to a conclusion that photoresponse degradation in C-B region of phototransistor is the main contribution to CTR degradation of optocouplers.