4N26SM

Overview

The Fairchild Semiconductor 4N26SM is a general-purpose, single-channel transistor output optocoupler housed in a surface-mount DIP-6 package. It provides electrical isolation between input and output circuits using an infrared LED coupled to an NPN phototransistor. Key electrical specifications include a maximum forward current of 60 mA, a collector-emitter breakdown voltage of 30 V, and a minimum current transfer ratio of 20%. The device offers a high isolation voltage rating of 4170 Vrms (or 4200 V min) and operates within a temperature range of -40°C to +100°C.

Feature Summary

• Provides galvanic isolation for signal transmission between low-voltage control circuits and higher-voltage loads.
• Features a standard NPN phototransistor output suitable for interfacing with digital logic families.
• Designed for surface-mount assembly to facilitate compact PCB layouts.
• Complies with international safety standards including UL recognition and VDE approval.

Applications

• Signal isolation in industrial control systems
• Interface circuits for microcontrollers and PLCs
• Power supply feedback loops
• Switching applications requiring electrical isolation

Procurement Notes

Verify the manufacturer marking on the component body, as both Fairchild Semiconductor and onsemi produce this part number following corporate acquisitions. Confirm the suffix 'SM' indicates the specific surface-mount DIP-6 package variant rather than through-hole versions. Ensure the datasheet version matches the required isolation voltage ratings and safety certifications for your specific application compliance needs.

Selection Notes

Select this component when a cost-effective, general-purpose optocoupler with moderate speed and high isolation voltage is required. It is suitable for applications where the 2 µs switching time is sufficient. Consider alternative packages if surface-mount constraints are not met, or choose devices with higher current transfer ratios if driving heavy loads directly from the phototransistor collector.

Part Context

The 4N26 series is a widely recognized family of general-purpose optocouplers originally introduced by Fairchild Semiconductor. The 4N26SM specifically denotes the surface-mount variant of the classic 4N26 through-hole device. This component remains a standard reference design in many electronic schematics for basic isolation tasks due to its long-standing availability and predictable performance characteristics across various operating conditions.

Replacement Considerations

Direct pin-compatible replacements include the 4N25SM and 4N27SM, though their current transfer ratios differ. Verify that substitute parts meet the same 4170 Vrms isolation requirement and operate within the -40°C to +100°C temperature range. Always consult the specific datasheet of the replacement component to ensure compatibility with existing circuit biasing conditions.