5300Vrms isolation in a through-hole DIP
The H11A3300 is a single-channel phototransistor optoisolator from onsemi, packing 5300Vrms of galvanic isolation into a standard 6-DIP through-hole package. That isolation rating means it cleanly separates a low-voltage control side from a higher-voltage load side — think microcontroller GPIO driving a 24V PLC input or a 120VAC relay coil — without a shared ground path.
CTR and switching speed for the BOM
With a minimum current transfer ratio of 20% at 10mA forward current, the H11A3300 guarantees the output transistor turns on hard enough to saturate a downstream logic input or a base-biased transistor stage. The 2µs typical turn-on and turn-off times keep it fast enough for 100kHz-ish signal isolation — plenty for serial data, PWM feedback, or status polling across an isolation barrier.
onsemi lists the H11A3300 as obsolete.