Equivalent & Substitute Parts for 4N37 Optoisolator

Part Overview

The 4N37 is a single-channel optoisolator transistor with base output, designed for high-voltage isolation applications. The onsemi 4N37 (Obsolete status) provides 5300Vrms isolation with a 6-DIP through-hole package. Due to its obsolete product status, equivalent and substitute parts are necessary for ongoing production and maintenance applications. Active alternatives with comparable electrical characteristics and identical mechanical packaging are available from multiple manufacturers.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N37
Manufacturer	onsemi
Category	Optoisolators
Package / Case	6-DIP (0.300", 7.62mm)
Mounting Type	Through Hole
Number of Channels	1
Voltage - Isolation	5300Vrms
Output Type	Transistor with Base
Voltage - Output (Max)	30V
Current Transfer Ratio (Min)	100% @ 10mA
Voltage - Forward (Vf) (Typ)	1.18V
Current - DC Forward (If) (Max)	100 mA
Vce Saturation (Max)	300mV
Turn On / Turn Off Time (Typ)	2µs, 2µs
Operating Temperature	-55°C ~ 100°C
Product Status	Obsolete
REACH Status	REACH Unaffected
ECCN	EAR99

Substitute Part Grouping Explanation

Substitution for the 4N37 optoisolator is determined by the following critical parameters:

Mechanical Compatibility:

Package type: 6-DIP (0.300", 7.62mm) through-hole mounting
Pin count and spacing must match for direct PCB compatibility

Electrical Compatibility:

Isolation voltage: Minimum 4170Vrms (acceptable reduction from 5300Vrms for most applications)
Output type: Transistor with base configuration
Maximum output voltage: 30V or higher
Current transfer ratio: Minimum 20% @ specified input current
Operating temperature range: -40°C to 100°C minimum

Regulatory Compliance:

RoHS3 compliance preferred for active parts
REACH compliance maintained across all alternatives

Substitute parts are grouped into two categories: direct manufacturer equivalents (same base part number with variant codes) and similar cross-manufacturer alternatives (different part numbers with compatible electrical and mechanical specifications).

Parameter Comparison

Part Number	Manufacturer	Voltage - Isolation	Current Transfer Ratio (Min)	Voltage - Output (Max)	Vce Saturation (Max)	Turn On / Turn Off Time (Typ)	Operating Temperature	Product Status	Package
4N37	onsemi	5300Vrms	100% @ 10mA	30V	300mV	2µs, 2µs	-55°C ~ 100°C	Obsolete	6-DIP
4N37M	onsemi	4170Vrms	100% @ 10mA	30V	300mV	2µs, 2µs	-40°C ~ 100°C	Active	6-DIP
4N37-X000	Vishay Semiconductor Opto Division	5000Vrms	100% @ 10mA	30V	—	10µs, 10µs	-55°C ~ 100°C	Active	6-DIP
4N35-000E	Broadcom Limited	3550Vrms	100% @ 10mA	30V	300mV	—	-55°C ~ 100°C	Active	6-DIP
H11AG1M	onsemi	4170Vrms	100% @ 1mA	30V	400mV	5µs, 5µs	-40°C ~ 100°C	Active	6-DIP
H11D3M	onsemi	4170Vrms	20% @ 10mA	200V	400mV	5µs, 5µs	-40°C ~ 100°C	Active	6-DIP
MCT5210M	onsemi	4170Vrms	70% @ 3mA	30V	400mV	10µs, 400ns	-40°C ~ 100°C	Active	6-DIP
MOC8204M	onsemi	4170Vrms	20% @ 10mA	400V	400mV	5µs, 5µs	-40°C ~ 100°C	Active	6-DIP

Engineering Selection Recommendations

Direct Replacement (Preferred): The 4N37M from onsemi is the primary direct substitute. It maintains the same base part number family, identical current transfer ratio specification (100% @ 10mA), matching output voltage rating (30V), and identical saturation voltage (300mV). The isolation voltage reduction from 5300Vrms to 4170Vrms is acceptable for applications not requiring the full 5300Vrms specification. This part is RoHS3 compliant and carries Active product status.

Alternative from Vishay: The 4N37-X000 from Vishay Semiconductor Opto Division provides 5000Vrms isolation, closely matching the original specification. It maintains 100% current transfer ratio and 30V output voltage. Operating temperature range matches the original (-55°C to 100°C). This part is RoHS3 compliant and Active.

Cross-Manufacturer Alternatives: The 4N35-000E (Broadcom Limited) offers lower isolation voltage (3550Vrms) but maintains 100% current transfer ratio and identical output voltage. Selection depends on application isolation requirements.

The H11AG1M, H11D3M, MCT5210M, and MOC8204M provide alternative electrical characteristics with different current transfer ratios, output voltage ratings, and switching times. These are suitable only when application requirements align with their specific parameter sets.

Compliance Consideration: All active substitute parts carry RoHS3 compliance and REACH Unaffected status, meeting modern regulatory requirements. The original 4N37 (Obsolete) does not carry RoHS3 certification.

Frequently Asked Questions (FAQ)

Q: Can I directly replace the obsolete 4N37 with the 4N37M? A: Yes. The 4N37M is the direct onsemi substitute with identical package, pin configuration, and core electrical characteristics. The isolation voltage is reduced from 5300Vrms to 4170Vrms, which is acceptable for most applications. Verify your circuit does not require the full 5300Vrms isolation specification.

Q: What is the difference between the 4N37 and 4N37-X000? A: Both are 6-DIP through-hole optoisolators with 100% current transfer ratio and 30V output voltage. The 4N37-X000 is manufactured by Vishay and provides 5000Vrms isolation (versus 5300Vrms for the original). The 4N37-X000 has slower switching times (10µs versus 2µs). Select based on isolation voltage and switching speed requirements.

Q: Why do some substitutes have lower current transfer ratios? A: Current transfer ratio (CTR) varies by part design and is specified at different input currents. The H11D3M and MOC8204M specify 20% CTR @ 10mA, which is lower than the 4N37's 100% @ 10mA. These parts are suitable only if your circuit design accommodates lower CTR values. Do not use as direct replacements if your design requires 100% CTR.

Q: Can I use the H11D3M or MOC8204M as substitutes? A: These parts share the 6-DIP package and 4170Vrms isolation voltage but have significantly different electrical characteristics. The H11D3M supports 200V output (versus 30V), and MOC8204M supports 400V output. Both have lower current transfer ratios (20% @ 10mA). Use only if your application specifically requires these higher output voltage ratings and can operate with lower CTR.

Q: Are all substitute parts RoHS3 compliant? A: All active substitute parts listed (4N37M, 4N37-X000, 4N35-000E, H11AG1M, H11D3M, MCT5210M, MOC8204M) are RoHS3 compliant. The original 4N37 (Obsolete) is not RoHS3 certified. For new designs and production, select from the active, RoHS3-compliant alternatives.

Q: What is the operating temperature difference between the 4N37 and its substitutes? A: The original 4N37 operates from -55°C to 100°C. Most active substitutes (4N37M, H11AG1M, H11D3M, MCT5210M, MOC8204M) operate from -40°C to 100°C, a 15°C reduction at the lower end. The 4N37-X000 and 4N35-000E maintain the full -55°C to 100°C range. Select based on your application's minimum operating temperature requirement.

Q: Can I mix different substitute parts in the same circuit board? A: All listed substitutes use the 6-DIP through-hole package with identical pin spacing and can be physically installed in the same PCB footprint. However, electrical characteristics vary significantly. Use the same part number across all positions in a design unless your circuit specifically accommodates parameter variations.

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