CONTROL CIRCUIT INITIATING CONDUCTION OF AN OPTO- ISOLATOR UNIT

摘要

CONTROL CIRCUIT INITIATING CONDUCTION OF AN OPTO-ISOLATOR UNIT A control circuit for turning on an optical isolation unit only when an input signal is at least of a given magnitude or threshold level. The circuit exhibits a resistive input below the threshold level and a constant current characteristic above the threshold. An arrangement of transistors is provided to bypass the opto-isolator below the threshold and to drive the opto-isolator with substantially constant current above the threshold.