4N24ATX

Overview

The 4N24ATX is a high-reliability optically coupled isolator manufactured by TT Electronics/Optek Technology. It integrates an infrared emitting diode and an NPN silicon phototransistor within a hermetically sealed TO-78 package. The device provides 1 kV electrical isolation between input and output circuits. Key electrical parameters include a maximum collector-emitter voltage of 35 V, a DC forward current limit of 40 mA, and a typical rise/fall time of 20 µs. It features a base contact for transistor biasing and operates within a temperature range of -65°C to 125°C.

Feature Summary

• Hermetically sealed TO-78 metal can package designed for military and harsh environments
• High current transfer ratio with integrated base contact for conventional transistor biasing
• 1 kV electrical isolation capability between input and output channels

Applications

• High-voltage isolation between input and output circuits
• Electrical isolation in electrically noisy or dirty industrial environments
• Medical equipment signal isolation
• Office equipment interface protection

Procurement Notes

Verify the specific suffix (TX vs TXV) against the design requirement, as processing standards differ. Confirm RoHS compliance status if required, as military screening variants may not adhere to standard environmental directives. Ensure the TO-78 through-hole mounting style matches the PCB layout. Validate that the 1 kV isolation rating meets the system safety requirements.

Selection Notes

Select this component when high reliability and radiation hardness are critical. The TO-78 package offers superior environmental sealing compared to plastic packages. The included base terminal allows for improved switching speed control via external biasing. Verify that the 35 V collector-emitter voltage is sufficient for the load application. Consider the 20 µs switching speed for frequency limitations.

Part Context

This part belongs to the 4N22-24 series of high-reliability optocouplers from TT Electronics/Optek Technology. These devices are processed according to MIL-PRF-19500 standards. The series includes variants like 4N22, 4N24, and their TX/TXV derivatives. They are distinct from commercial grade optocouplers due to the hermetic packaging and rigorous screening processes.

Replacement Considerations

The 4N24A is listed as a parameter-equivalent substitute. Verify if the non-TX suffix meets the same military screening requirements. Cross-reference pinouts and mechanical dimensions to ensure compatibility with existing footprints.