| 摘要 |
<p>PURPOSE:To prevent a common mode noise from the input side from being delivered to the output side by providing a circuit comparing the output potential of a photodiode continuity detection switching element of a photocoupler with an output potential of an amplifier of the photocoupler. CONSTITUTION:With a noise given from the input side, a current flows to a base of as transistor(TR) 13 of the photocoupler 1 through a stray capacitor between the input side and the base of the TR 13 and the collector-emitter junction of the TR 13 is energized, but since no current flows to a photo diode 12 of the photocoupler 1, the collector-emitter junction of a PNP TR 5 remains nonconductive, the potential E1 of a node 25 is EON and the potential E2 of a node 24 goes a low level (=0V) because of a pull-down resistor 6. Thus, the output 23 goes to a high level, and it is similar to the case with a light emitting element 11 in non-continuity.</p> |
