7500Vpk isolation in a 6-DIP through-hole package
The onsemi H11A3TM is a single-channel optocoupler with a DC input LED and a phototransistor output that includes a base connection. Its headline rating is 7500Vpk isolation voltage, which qualifies it for reinforced insulation in mains-powered equipment where the safety barrier must withstand high-voltage transients without breakdown. The 6-DIP (0.400", 10.16mm) through-hole package suits designs where the optocoupler is hand-loaded or reworked in a production line that avoids surface-mount. The 6-DIP supplier device package matches the standard DIP-6 footprint used across the H11A series, so the PCB layout is shared with other CTR or output variants.
CTR floor and switching speed for signal isolation
The minimum current transfer ratio is 20% at 10 mA forward current. This means the phototransistor collector current is at least 2 mA when the LED is driven at 10 mA, setting the minimum load current the output can sink. Designs with high-impedance pull-ups or low-gain downstream stages must stay above this floor to guarantee logic-level switching across temperature. Turn-on and turn-off times are 2 µs typical each, giving a combined propagation delay of about 4 µs. This is fast enough for 100 kHz signal isolation or for debouncing digital inputs in industrial control, but not for high-speed data links above 1 Mbps. The Vce saturation is 400 mV max at the rated output current, so the output drops less than half a volt when the transistor is fully on. This keeps the logic-low level well below the 0.8 V threshold of a standard TTL input, ensuring clean signal transfer across the isolation barrier.
onsemi has marked the H11A3TM as obsolete. Existing BOM lines that require this specific CTR grade and package can be sourced through independent distribution channels against an RFQ. The 30 V max output voltage limits the collector supply to low-voltage logic rails or 24 V industrial buses.