Switching characteristics of crossed-film cryotron circuits

Recent interest in crossed-film cryotron circuits for combined logic and memory applications has prompted a detailed investigation of their switching characteristics. Experimental measurements show that the switching characteristics depend markedly on current level, driving pulse shape, interaction of successive circuit stages, and operating temperature. For example, increasing the current from 10 to 50 percent above the minimum required for operation, reduced switching delay from about 100 to less than 10 ns. This improvement in switching behavior is explained. Also, in a three-stage flip-flop circuit, decreasing the current in the second stage increased the switching time of the first and third as well as the switching time of the second stage. This investigation indicates that in most crossed-film cryotron circuit applications, switching delays other than circuit time constants can be largely eliminated if adequate current tolerances can be maintained.