Isolation and signal transfer — the specs that decide fit
The H11A617A300W: Rated for 5300Vrms galvanic isolation, this optocoupler provides safe signal separation between a DC input and a phototransistor output in a single-channel 4-DIP package. The 40% to 80% current transfer ratio at 10mA forward current defines the minimum output drive — at 40% CTR, a 10mA input yields 4mA at the collector, enough to pull a TTL or CMOS logic input low through a pull-up resistor. The 70V output breakdown and 50mA continuous output current suit it for driving relay coils, PLC digital inputs, or low-power DC loads.
Temperature and switching — the operating envelope
The -55°C to 100°C operating temperature range covers industrial and military-grade environments — think motor-drive feedback, power-supply regulation loops, or isolated sensor interfaces in outdoor cabinets. Typical rise and fall times of 2.4µs limit the usable data rate to roughly 100 kbit/s; this is a DC-to-low-frequency isolator, not a high-speed digital coupler. The 400mV max Vce saturation keeps the on-state voltage drop low when the output transistor is fully turned on, minimising power dissipation in the output stage.