4170Vrms isolation for industrial signal transfer
The 4N38VM is a single-channel optoisolator from onsemi that passes a 4170Vrms isolation barrier between a DC LED input and a phototransistor output with a base terminal. The base pin lets you tailor the switching threshold or add a speed-up capacitor — useful when the downstream logic has a slow input rise-time spec.
Minimum current transfer ratio is 20% at 10 mA forward current. At 10 mA LED drive, the output transistor can sink at least 2 mA into the collector load. If your load resistor pulls 5 mA, you need to increase the LED current or pick a higher-CTR part — the 4N38VM does not guarantee margin there. Typical turn-on and turn-off times are both 5 µs. That places the 4N38VM in the low-speed isolation zone — fine for 50/60 Hz mains zero-cross detect, relay coil drive, or PLC digital input sampling at a few kHz. Do not expect it to pass a 100 kHz PWM signal without pulse-width distortion. Output transistor is rated for 80 V collector-emitter and 100 mA continuous current. The 1 V max Vce(sat) at the rated current means about 100 mW conduction loss in the output stage — well within the DIP package's thermal budget at 100°C ambient.
Active production — 6-DIP through-hole, Bulk packaging
onsemi lists the 4N38VM as Active and ROHS3 compliant. Through-hole 6-DIP package with 0.300-inch body width — standard footprint that mates with sockets or solders directly into plated through-holes. For high-volume pick-and-place, check the 4N38V or 4N38SMT variants if they carry the same isolation and CTR ratings.