4N31

Overview

The Everlight 4N31 is a single-channel phototransistor output optocoupler featuring a GaAs infrared LED emitter and a Darlington photodetector. It provides high isolation voltage of 5000 Vrms. Key electrical parameters include a collector-emitter saturation voltage of 1.2 V maximum, forward voltage of 1.5 V, and reverse voltage of 6 V. The device exhibits a rise time of 25 µs and fall time of 18 µs. Power dissipation is rated at 200 mW. It is available in a 6-pin DIP package with wide-lead spacing options.

Feature Summary

• Integrates a GaAs infrared emitting diode with a high-gain Darlington phototransistor detector for enhanced signal transmission.
• Provides robust electrical isolation capability suitable for separating circuits with significant potential differences.
• Features a base pin on the photodetector to allow for external biasing or speed adjustment.

Applications

• Signal isolation in industrial control systems
• Interface between microprocessors and power switching circuits
• Solid-state relay driver applications

Procurement Notes

Verify the specific suffix (e.g., -V) against the manufacturer's current datasheet to confirm lead frame plating and RoHS compliance status. Ensure the selected package variant matches the required PCB footprint, as wide-lead spacing options may differ from standard DIP dimensions. Confirm availability through authorized distributors due to potential supply constraints.

Selection Notes

Select this component when high gain is required due to the Darlington configuration, accepting the trade-off of slower switching speeds compared to standard phototransistors. Verify that the 5000 Vrms isolation rating meets the safety requirements of the target application. Consider the 200 mW power dissipation limit during thermal analysis for enclosed environments.

Part Context

The 4N31 belongs to the family of general-purpose transistor-output optocouplers manufactured by Everlight Electronics. These devices are widely used for basic galvanic isolation tasks. The 4N31 specifically utilizes a Darlington output structure, distinguishing it from standard phototransistor variants like the 4N25 by offering higher current transfer ratio at the cost of increased propagation delay.

Replacement Considerations

Direct replacements include the 4N35 and 4N37, which share similar pinouts and functional characteristics but may vary in current transfer ratio specifications. Verify compatibility with existing circuit designs before substitution.