| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-reliability and fail-safe majority circuit with which the generation probability of H-side fault is remarkably reduced. SOLUTION: This majority circuit is composed of AND 11, 12 and 13 for inputting two of three inputs ina, inb and inc and an OR 20. When the inputs more than two are H, the output of the majority circuit becomes H and an optical thyristor is ignited. The AND 11 is composed of open drain buffers 31 and 32 for inputting ina and inb, a resistor 41 for pull-up to be connected with the common output terminal of both the buffers, and a light emitting diode. Therefore, the AND 11-13 can be constituted as asymmetric fault elements for which the generation probability of H-side fault is extremely low. The OR 20 is constituted by respectively confronting the respective incident terminals of optical fibers 61-63 with light emitting diodes 51-53 and simultaneously confronting the respective emitting terminals to the optical thyristor 70. Therefore, this OR can be composed of only inactive elements and constituted as a rare fault element. |
