The TLP291(GB,SE is a single-channel DC-input, transistor-output optocoupler from Toshiba in a 4-SOIC surface-mount package. Its 3750Vrms isolation rating suits basic or functional isolation in industrial controls, PLC I/O modules, motor-drive feedback, and isolated sensor interfaces where the signal path needs a galvanic barrier without the footprint of a DIP-8. The transistor output with a minimum current transfer ratio of 100% and maximum of 600% at 5 mA forward current gives you headroom to drive logic inputs or small relays directly, while the 80 V output rating handles higher-side switching in 24 V or 48 V industrial rails.
Combined with ROHS3 compliance, this part is qualified for ongoing design-in and production without a forced migration timeline. For dual-sourcing flexibility, the TLP291 family includes CTR-binned variants such as TLP291(GR,SE (lower CTR range) and TLP291(BL-TP,SE (higher CTR range), all sharing the same 4-SOIC footprint and 3750Vrms isolation rating.
Switching speed and CTR — sizing the drive margin
That is adequate for isolated digital inputs, relay coil drives, and slow serial buses where the propagation delay is not the timing bottleneck. The 100% minimum CTR at 5 mA forward current means a 5 mA input can deliver at least 5 mA at the output — enough to saturate the transistor and pull a 5 V logic input low with margin. The 300 mV max Vce saturation keeps the on-state voltage drop low, so the output can sink the rated 50 mA per channel without excessive dissipation.
Temperature range and mounting
The 4-SOIC package (4.55 mm body width) is a compact footprint for high-density boards, and the surface-mount format aligns with standard reflow processes. The Tube shipping medium is typical for engineering samples and low-volume production; reeled options (e.g., TLP291(GRL-TP,SE) are available for higher-volume pick-and-place.