4N38S Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N38S is an optoisolator transistor with base output manufactured by onsemi, rated for 5300Vrms isolation voltage in a 6-SMD surface mount package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The 4N38S provides single-channel isolation with transistor output and base connection, suitable for applications requiring galvanic isolation in DC input circuits.

Substiute Parts

4N38S

onsemiIn Stock: 7314N38S Datasheet

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4N38SM

onsemiIn Stock: 125964N38SM Datasheet

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4N38SM

onsemiIn Stock: 125964N38SM Datasheet

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4N38SMT&R

Isocom Components 2004 LTDIn Stock: 11024N38SMT&R Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the 4N38S is determined by the following critical parameters:

• Number of Channels: Must be 1 (single channel)
• Output Type: Must be Transistor with Base
• Package / Case: Must be 6-SMD, Gull Wing (surface mount compatibility)
• Voltage - Output (Max): Must be ≥80V
• Current - Output / Channel: Must be ≥100mA
• Current Transfer Ratio (Min): Must be ≥20% @ 10mA
• Vce Saturation (Max): Must be ≤1V
• Input Type: Must be DC

The 4N38S has two identified substitute parts: 4N38SM (onsemi, active status) and 4N38SMT&R (Isocom Components 2004 LTD, active status). Both maintain the core functional parameters and package configuration, with variations in isolation voltage rating and operating temperature range.

Parameter Comparison

Engineering Selection Recommendations

4N38SM (onsemi): This substitute maintains active product status with ROHS3 compliance. The isolation voltage is reduced to 4170Vrms compared to the 4N38S rating of 5300Vrms. The operating temperature range is narrower (-40°C to 100°C versus -55°C to 100°C). Selection of 4N38SM is appropriate for applications where the lower isolation voltage and reduced low-temperature operating range are acceptable within the circuit design margins.

4N38SMT&R (Isocom Components 2004 LTD): This substitute is supplied in Tape & Reel packaging format and maintains active product status with ROHS3 compliance. The isolation voltage specification differs significantly (7.5Vpk). The output current per channel is reduced to 50mA compared to the 4N38S specification of 100mA. The operating temperature range matches the 4N38S (-55°C to 100°C). Selection of 4N38SMT&R requires confirmation that the reduced output current capacity and different isolation voltage specification are compatible with the application requirements.

Frequently Asked Questions (FAQ)

Q: Can 4N38SM directly replace 4N38S in all applications?

A: 4N38SM maintains functional compatibility in package, channel count, output type, and core electrical parameters. However, the isolation voltage is lower (4170Vrms vs. 5300Vrms) and the operating temperature minimum is higher (-40°C vs. -55°C). Substitution is valid only if the application does not require the higher isolation voltage or extended low-temperature operation of the original 4N38S.

Q: What are the limitations of 4N38SMT&R as a substitute?

A: The 4N38SMT&R has a maximum output current of 50mA per channel, which is half the 4N38S specification of 100mA. Applications requiring the full 100mA output current cannot use this substitute. The isolation voltage specification (7.5Vpk) also differs from the 4N38S (5300Vrms), requiring circuit-level evaluation.

Q: Are both substitutes available in the same packaging format?

A: Both 4N38SM and 4N38SMT&R use 6-SMD, Gull Wing surface mount packages. The primary packaging difference is that 4N38SMT&R is supplied in Tape & Reel format, while 4N38SM is supplied in Bulk format. Both are compatible with standard surface mount assembly processes.

Q: What compliance certifications apply to these substitutes?

A: Both 4N38SM and 4N38SMT&R are ROHS3 compliant and REACH unaffected. The original 4N38S does not specify RoHS status. All three parts share the same ECCN (EAR99) and HTSUS (8541.49.8000) classifications.

Q: How do the turn-on and turn-off times compare?

A: The 4N38S and 4N38SM both specify 5µs turn-on and turn-off times. The 4N38SMT&R does not specify turn-on/turn-off time but provides rise and fall times of 2µs each. For timing-critical applications, the 4N38SMT&R may offer faster switching characteristics based on the rise/fall time specification.