Isolation and signal transfer for industrial logic interfaces
The onsemi 4N26TVM is a single-channel optoisolator in a through-hole 6-DIP package, built for breaking ground loops and level-shifting digital signals in industrial control, PLC, and motor-drive feedback circuits. Its 4170Vrms isolation rating means the input and output sides are galvanically separated — a 24V PLC input stage won't couple fault current back to the 5V logic side during a surge event.
CTR, switching speed, and what they mean for the BOM
Minimum current transfer ratio is 20% at 10mA forward current — at 10mA in, the output transistor can sink at least 2mA collector current, which is enough to pull a standard TTL or CMOS input low through a 10kΩ pull-up to 5V. Typical turn-on and turn-off times are 2µs each — this opto switches fast enough for 100kHz serial data or PWM feedback, but the 2µs propagation delay means the downstream logic sees the signal two microseconds after the LED fires. Vce saturation is 500mV max at the rated collector current — the output drops half a volt when fully on, so the logic-low voltage at the receiver stays well below the 0.8V TTL threshold even with a light pull-up.