Trends in optocoupler radiation degradation

Proton-radiation test results for new optocoupler technologies are compared with those of older optocouplers. The new devices are far more resistant to displacement damage effects and have a much higher current-transfer ratio (CTR). The improvements are due to improved optical-coupling efficiency in combination with light-emitting diode (LED) technologies that are inherently more resistant to lifetime degradation. Because of these changes, CTR degradation is no longer dominated by LED damage. LED degradation, gain degradation, and photoresponse degradation all contribute to the overall changes in CTR after irradiation in the newer device types.