Darlington gain at low LED drive
The TLP387(D4-TPL,E delivers a minimum current transfer ratio of 1000% at just 1 mA forward current — that is a gain of 10× from LED input to collector output. For a design that needs to switch a 150 mA load from a logic-level output that can only source a couple milliamps, this part avoids adding a second driver transistor.
5000 Vrms isolation for mains-tied interfaces
Rated at 5000 Vrms isolation, this optocoupler can sit between a 240 VAC line and a 3.3 V microcontroller without the creepage distance becoming a board-layout headache. The 6-SOIC 4-lead package (0.173-inch body width) keeps the footprint compact while maintaining the reinforced isolation barrier.
300 V output ceiling and switching speed
The output transistor is rated for 300 V maximum collector-emitter voltage and 150 mA continuous current. Turn-on time is 50 µs typical, turn-off 15 µs typical — fast enough for 50/60 Hz line-synchronous switching or relay-coil drive, but not for high-frequency PWM. The 1 V Vce(sat) maximum at rated current means the Darlington drop is higher than a single transistor; budget the power dissipation in the output stage.
The tape-and-reel variant (D4 suffix) is the standard ordering option for automated pick-and-place assembly.