4N37W Equivalent & Substitute Parts

Part Overview

The 4N37W is an optoisolator transistor with base output manufactured by onsemi, rated for 5300Vrms isolation voltage in a 6-DIP package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 4N37W provides single-channel DC input isolation with transistor output including base connection, suitable for applications requiring galvanic isolation with direct transistor control capability.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N37W
Manufacturer	onsemi
Category	Optoisolators
Package / Case	6-DIP (0.400", 10.16mm)
Number of Channels	1
Voltage - Isolation	5300Vrms
Current Transfer Ratio (Min)	100% @ 10mA
Output Type	Transistor with Base
Voltage - Output (Max)	30V
Voltage - Forward (Vf) (Typ)	1.18V
Current - DC Forward (If) (Max)	100 mA
Vce Saturation (Max)	300mV
Operating Temperature	-55°C ~ 100°C
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the 4N37W is determined by the following critical parameters:

Package compatibility: 6-DIP form factor with 0.400" (10.16mm) pitch
Isolation voltage: Minimum 5000Vrms to maintain equivalent isolation performance
Output configuration: Transistor with base connection for direct gate/base drive capability
Current transfer ratio: Minimum 100% @ 10mA for consistent switching behavior
Operating temperature range: Support for -55°C to 100°C envelope
Input type: DC input isolation
Output voltage rating: 30V maximum

Three substitute parts meet these criteria with varying isolation voltage ratings and thermal specifications. All substitutes maintain the 6-DIP package, single-channel transistor output with base, and DC input isolation required for functional equivalence.

Parameter Comparison

Parameter	4N37W (Main)	4N37-X006	4N37G	4N37M
Manufacturer	onsemi	Vishay Semiconductor Opto Division	Isocom Components 2004 LTD	onsemi
Product Status	Obsolete	Active	Active	Active
Package / Case	6-DIP (0.400", 10.16mm)	6-DIP (0.400", 10.16mm)	6-DIP (0.400", 10.16mm)	6-DIP (0.300", 7.62mm)
Number of Channels	1	1	1	1
Voltage - Isolation	5300Vrms	5000Vrms	7.5Vpk	4170Vrms
Current Transfer Ratio (Min)	100% @ 10mA	100% @ 10mA	100% @ 10mA	100% @ 10mA
Output Type	Transistor with Base	Transistor with Base	Transistor with Base	Transistor with Base
Voltage - Output (Max)	30V	30V	30V	30V
Voltage - Forward (Vf) (Typ)	1.18V	1.2V	1.2V	1.18V
Current - DC Forward (If) (Max)	100 mA	60 mA	50 mA	60 mA
Vce Saturation (Max)	300mV	Not Specified	300mV	300mV
Operating Temperature	-55°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 100°C	-40°C ~ 100°C
Turn On / Turn Off Time (Typ)	2µs, 2µs	10µs, 10µs	Not Specified	2µs, 2µs
RoHS Status	Not Specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

4N37-X006 (Vishay Semiconductor Opto Division): Active product status with ROHS3 compliance. Isolation voltage of 5000Vrms meets minimum substitution threshold. Turn-on/turn-off time of 10µs is slower than the original 2µs specification. Forward current maximum of 60 mA is reduced from 100 mA. Suitable for applications where switching speed is not critical and reduced input current is acceptable.

4N37G (Isocom Components 2004 LTD): Active product status with ROHS3 compliance. Isolation voltage specified as 7.5Vpk does not meet the 5000Vrms minimum isolation requirement for direct substitution. This part is not recommended as a functional equivalent due to insufficient isolation voltage rating.

4N37M (onsemi): Active product status with ROHS3 compliance. Isolation voltage of 4170Vrms is below the 5300Vrms rating of the original part. Operating temperature minimum of -40°C is higher than the -55°C specification. Package pitch of 0.300" (7.62mm) differs from the original 0.400" (10.16mm), requiring PCB layout modification. Turn-on/turn-off time of 2µs matches the original specification. Forward current maximum of 60 mA is reduced from 100 mA.

Frequently Asked Questions (FAQ)

Q: Can 4N37-X006 directly replace 4N37W in all applications?

A: 4N37-X006 maintains functional compatibility for isolation voltage, output configuration, and operating temperature range. However, the increased turn-on/turn-off time (10µs versus 2µs) and reduced forward current maximum (60 mA versus 100 mA) may affect performance in high-speed switching or high-current input applications. Circuit validation is necessary for timing-critical designs.

Q: Why is 4N37G not recommended as a substitute?

A: The 4N37G isolation voltage specification of 7.5Vpk is insufficient compared to the 4N37W requirement of 5300Vrms. This represents a significant reduction in isolation capability and does not meet the substitution criteria for this product category.

Q: What are the package differences between 4N37M and 4N37W?

A: The 4N37M uses a 6-DIP package with 0.300" (7.62mm) pitch, while the 4N37W uses 0.400" (10.16mm) pitch. This physical difference requires PCB footprint modification and cannot be used as a direct pin-compatible replacement without layout redesign.

Q: Are all substitute parts RoHS compliant?

A: Yes. 4N37-X006, 4N37G, and 4N37M are all ROHS3 compliant. The original 4N37W does not specify RoHS status.

Q: Which substitute part has the closest electrical performance to 4N37W?

A: 4N37M matches the turn-on/turn-off time specification (2µs) and Vce saturation (300mV) of the original part. However, its lower isolation voltage (4170Vrms) and different package pitch limit its use as a direct replacement.

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