Proton damage in linear and digital optocouplers

Fundamental differences in design influence the way that linear and digital optocouplers are degraded by radiation. Linear optocouplers are more affec ted by current drive conditions because the detector operates in a high-inj ection region when the LED produces normal light output, and do not have th e extra operating margin that is inherent in digital optocouplers. Although LED degradation is often the dominant degradation mechanism in space envir onments, degradation of optocouplers with improved LEDs is limited by photo response degradation. Phototransistor gain has a relatively minor effect ex cept at very high radiation levels.