4170 Vrms isolation in a DIP-6 package
The onsemi 4N37TVM is a single-channel optoisolator with a DC input LED and a phototransistor output that includes a base terminal, packaged in a 6-DIP (0.400", 10.16 mm) through-hole body. Rated for 4170 Vrms isolation between input and output, this part suits applications where galvanic separation is needed to protect low-voltage control logic from higher-voltage transients on the load side.
CTR and switching — what the numbers mean for your circuit
Minimum current transfer ratio of 100% at 10 mA forward current means the phototransistor collector current will be at least equal to the LED drive current — a 10 mA input yields 10 mA output drive, enough to saturate a downstream logic input without additional gain stage. Typical turn-on and turn-off times of 2 µs each set the practical data rate ceiling around 250 kbps in a saturated switch configuration; for faster edges, the base terminal allows external base-emitter resistor tuning to trade off speed against noise margin. Maximum Vce saturation of 300 mV at the rated output current keeps the voltage drop low when the transistor is fully on, preserving headroom for the downstream load.