Isolation and switching margins
The SFH601-1: That 2:1 spread means the LED drive current must be set so the worst-case minimum CTR still saturates the output transistor into the logic or relay load. With Vce(sat) clamped at 400 mV max, the output pulls within 0.4 V of the rail — clean enough to drive a TTL or CMOS input without a Schmitt trigger. Switching times are 2 µs typical rise and fall, with turn-on at 3 µs and turn-off at 2.3 µs. This places the useful data rate below about 100 kbit/s in a typical 24 V PLC input or isolated gate-drive application — fast enough for 1 kHz PWM but not for a high-speed serial link.
Temperature grade and package fit
Operating temperature spans -55 to 100 °C, covering the industrial equipment range including unheated enclosures and motor-bay compartments. The transistor output with base pin allows the designer to add a base resistor for speed-up or to bias the phototransistor for higher gain — a flexibility not available in Darlington or logic-output optos. The 2.54 mm pin pitch and 7.62 mm row spacing fit a 0.1-inch prototype board or a wave-solder production panel. Supplied in tube, so it feeds into automatic insertion equipment without reel-to-reel transfer.
Lifecycle and compliance
ROHS3 compliant, so no RoHS exemption tracking is needed for the BOM. The standard DIP-6 package and active status mean cross-shipments from multiple suppliers are straightforward to arrange.