4N29 Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N29 is a Darlington optoisolator manufactured by onsemi, featuring 5300Vrms isolation voltage and a 1-channel configuration in 6-DIP packaging. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The 4N29 provides Darlington output with base connection, suitable for applications requiring high isolation voltage and moderate output current capability.

Substiute Parts

4N29

onsemiIn Stock: 8694564N29 Datasheet

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4N29M

Fairchild SemiconductorIn Stock: 162094N29M Datasheet

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H11A1

onsemiIn Stock: 19937H11A1 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the 4N29 is determined by the following critical parameters:

• Isolation Voltage: Minimum 5000Vrms to maintain equivalent isolation performance
• Number of Channels: Must be 1 channel
• Output Type: Darlington with Base configuration required for pin compatibility
• Package Type: 6-DIP form factor for mechanical fit
• Operating Temperature Range: -55°C to 100°C minimum
• Input Type: DC input required
• Current Transfer Ratio: Minimum 50% @ 10mA acceptable for functional equivalence

The 4N29M and H11A1 meet these criteria with documented compatibility. The 4N29M maintains identical isolation voltage (5000Vrms minimum) and Darlington output configuration. The H11A1 provides equivalent isolation voltage with transistor output (rather than Darlington), requiring circuit evaluation for base drive requirements.

Parameter Comparison

Engineering Selection Recommendations

4N29M (Fairchild Semiconductor): This substitute maintains active product status, ensuring long-term availability and manufacturing support. It provides equivalent isolation voltage (5000Vrms), identical current transfer ratio (100% @ 10mA), and matching Darlington output configuration. The 6-DIP package dimension difference (0.400" vs. 0.300") requires PCB layout verification for mechanical clearance. Higher maximum output voltage (55V vs. 30V) provides additional design margin. ECCN and HTSUS classifications match the original part.

H11A1 (onsemi): This substitute offers equivalent isolation voltage (5300Vrms) and identical package dimensions (6-DIP 0.300"). However, the transistor output (rather than Darlington) and lower current transfer ratio (50% @ 10mA) necessitate circuit redesign for base drive requirements. Lower Vce saturation (400mV vs. 1V) may provide improved efficiency in switching applications. Product status is obsolete, limiting long-term procurement viability.

Frequently Asked Questions (FAQ)

Q: Can the 4N29M be used as a direct replacement for the 4N29?

A: The 4N29M is functionally equivalent for isolation voltage, channel count, and output type. However, the package dimension difference (0.400" vs. 0.300" DIP width) requires verification of PCB footprint compatibility. Electrical performance is equivalent or superior.

Q: What is the key difference between the 4N29 and H11A1?

A: The primary difference is output configuration. The 4N29 uses Darlington output, while the H11A1 uses transistor output. This affects base drive requirements and switching characteristics. The H11A1 has lower current transfer ratio (50% vs. 100%), requiring circuit evaluation before substitution.

Q: Are there isolation voltage differences between these parts?

A: The 4N29 and H11A1 both provide 5300Vrms isolation. The 4N29M provides 5000Vrms, which meets minimum isolation requirements but is 300Vrms lower. For applications with strict isolation margin requirements, the 4N29 or H11A1 are preferred.

Q: Which substitute has the best long-term availability?

A: The 4N29M carries active product status from Fairchild Semiconductor, indicating ongoing manufacturing and distribution support. Both the 4N29 and H11A1 are obsolete, limiting future procurement options.

Q: Do package differences affect circuit performance?

A: Package dimensions affect PCB layout and mechanical clearance only. Electrical performance is independent of DIP width variation. Verify PCB footprint compatibility before design implementation.