Circuit for testing opto-coupler having input, output, and control terminals

摘要

The test circuit involves the input terminals (11,12) of the opto-coupler (2) which are internally coupled to a light source (9), with the output terminals (14,15) coupled to a light detector (13) with an inner, controllable resistance, whose control terminal forms the opto-coupler control input (16). The inner resistance is rendered high-ohmic by an applied voltage independently of the light source state. A current (1) source is externally coupled to the input terminals. A recognition circuit (3) is externally coupled to the output terminals. A control voltage generator (3,27) is coupled to the control input, which transmits pulsed control signals to the opto-coupler for short-term, high-ohmic state of the inner resistance.