4170Vrms isolation for industrial noise separation
The 4N38SM is a single-channel phototransistor optocoupler from onsemi, rated for 4170Vrms isolation. That isolation rating suits it for breaking ground loops in motor-drive feedback, PLC digital inputs, and industrial sensor interfaces where transients can couple across a barrier. The output is a phototransistor with the base brought out, giving the designer the option to add a base-emitter resistor for faster turn-off or to bias the transistor for improved CTR linearity at low LED current.
CTR floor and forward current budget
Minimum current transfer ratio is 20% at 10 mA forward current. At that bias, the output can sink 2 mA into the load — enough to drive a 5 V logic input through a 2.2 kΩ pull-up. If the load needs more current, the 80 mA maximum DC forward current allows raising the LED drive, but the output transistor is limited to 100 mA continuous. Typical turn-on and turn-off times are both 5 µs, which keeps the opto transparent for 100 kHz PWM signals but will introduce noticeable skew in a 1 MHz data path. For 5 V logic interfaces at moderate speed (10–50 kHz), the 4N38SM is a clean fit.
Sourcing is straightforward through the open market; we can quote against your BOM quantity and confirm lead time at the time of the RFQ.
Surface-mount package and rework
The 6-SMD Gull Wing package has a 1.27 mm lead pitch — wide enough for hand soldering or hot-air rework without a stencil. The gull-wing leads are inspectable after soldering, which helps in prototype builds and low-volume production where X-ray inspection is not available. The 80 V output maximum gives headroom for 24 V and 48 V industrial rails, though the 100 mA output current limit means the opto is best used as a signal isolator rather than a power switch.