4N36FM Optoisolator - Equivalent & Substitute Parts

Part Overview

The 4N36FM is an optoisolator transistor with base output manufactured by onsemi, designed for high-voltage isolation applications. This component features a 7500Vpk isolation rating and is housed in a 6-SMD surface mount package. The 4N36FM is classified as obsolete, making identification of suitable substitute parts essential for ongoing design support and production continuity. Equivalent parts must maintain functional compatibility across isolation voltage, channel configuration, output type, and thermal operating range.

Substiute Parts

4N36FM

onsemiIn Stock: 10594N36FM Datasheet

Current PartRFQ

4N36SM

onsemiIn Stock: 221424N36SM Datasheet

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4N36

Texas InstrumentsIn Stock: 1004684N36 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 4N36FM is determined by the following critical parameters:

• Number of Channels: Must be 1 channel
• Output Type: Must be Transistor with Base
• Voltage - Isolation: Minimum 7500Vpk (or equivalent Vrms rating)
• Current Transfer Ratio (Min): 100% @ 10mA
• Voltage - Output (Max): 30V
• Operating Temperature Range: Must encompass -55°C ~ 100°C or be compatible with application requirements
• Mounting Type: Surface Mount preferred for direct replacement; Through Hole variants require PCB redesign

The 4N36FM has two identified substitute parts: the 4N36SM (onsemi, active status) and the 4N36 (Texas Instruments, active status). Both maintain the core functional parameters of single-channel transistor output optoisolation. However, isolation voltage ratings and package types differ, requiring engineering evaluation based on specific application constraints.

Parameter Comparison

Engineering Selection Recommendations

4N36SM (onsemi): This substitute maintains identical package geometry (6-SMD, Gull Wing) and switching characteristics (2µs turn-on/off times), enabling direct PCB replacement without layout modifications. However, the isolation voltage is reduced to 4170Vrms, which is lower than the 4N36FM's 7500Vpk rating. This part is active and available in high volume (22,100 pcs in stock). The operating temperature minimum is -40°C, which is 15°C higher than the 4N36FM. Selection of this part is appropriate only when application isolation voltage requirements do not exceed 4170Vrms and operating temperature does not fall below -40°C.

4N36 (Texas Instruments): This substitute provides an isolation voltage of 5000Vrms, which exceeds the 4N36SM but remains below the 4N36FM's 7500Vpk specification. The part is active with substantial inventory (100,400 pcs in stock) and maintains the full operating temperature range (-55°C ~ 100°C). However, this part uses a Through Hole 6-DIP package, requiring PCB redesign and cannot serve as a direct drop-in replacement. Switching speed is degraded (10µs turn-on/off times versus 2µs for the 4N36FM), and forward current is reduced to 50mA. This part is suitable for applications where isolation voltage requirements are met at 5000Vrms and PCB redesign is feasible.

Frequently Asked Questions (FAQ)

Q: Can the 4N36SM directly replace the 4N36FM on the existing PCB?

A: The 4N36SM shares identical package geometry (6-SMD, Gull Wing) and can be placed in the same footprint. However, the isolation voltage is reduced from 7500Vpk to 4170Vrms. Direct replacement is only valid if your application isolation voltage requirement does not exceed 4170Vrms and the minimum operating temperature does not fall below -40°C.

Q: Why does the Texas Instruments 4N36 have different switching times?

A: The Texas Instruments 4N36 exhibits 10µs turn-on and turn-off times compared to 2µs for the 4N36FM and 4N36SM. This difference is inherent to the device design and manufacturing process. Applications requiring faster switching response should not use this substitute without circuit redesign and timing analysis.

Q: What is the difference between Vpk and Vrms isolation voltage ratings?

A: Vpk (peak voltage) and Vrms (root mean square voltage) are different measurement standards for isolation voltage. The 4N36FM specifies 7500Vpk, while substitutes specify Vrms values. Direct voltage comparison requires conversion; however, the provided specifications use different standards and should be evaluated against your application's isolation voltage requirement in its specified form.

Q: Does the Texas Instruments 4N36 require PCB redesign?

A: Yes. The Texas Instruments 4N36 uses a Through Hole 6-DIP package, while the 4N36FM uses Surface Mount 6-SMD. PCB footprint, trace routing, and assembly process will require modification. This is not a direct replacement option for existing surface mount designs.

Q: Which substitute has the best availability?

A: The Texas Instruments 4N36 has the highest inventory at 100,400 pcs in stock, followed by the 4N36SM at 22,100 pcs. Both are active products with established supply chains.

Q: Is the 4N36SM RoHS compliant?

A: Yes, the 4N36SM is ROHS3 compliant. The 4N36FM does not specify RoHS status. The Texas Instruments 4N36 is RoHS non-compliant.