4N25TM Equivalent & Substitute Parts

Part Overview

The 4N25TM is an optoisolator transistor with base output manufactured by onsemi, designed for high-voltage isolation applications requiring 7500Vpk isolation rating. This component features a single-channel configuration in a 6-DIP package and is currently classified as obsolete. Due to its obsolete status, identifying equivalent and substitute parts is essential for ongoing system maintenance, redesign efforts, and procurement continuity. Substitute parts must maintain compatibility across isolation voltage, output characteristics, and package form factor while considering product availability and active manufacturing status.

Key Parameters

Parameter	4N25TM
Manufacturer	onsemi
Product Status	Obsolete
Number of Channels	1
Voltage - Isolation	7500Vpk
Current Transfer Ratio (Min)	20% @ 10mA
Output Type	Transistor with Base
Voltage - Output (Max)	30V
Voltage - Forward (Vf) (Typ)	1.18V
Current - DC Forward (If) (Max)	60 mA
Vce Saturation (Max)	500mV
Turn On / Turn Off Time (Typ)	2µs, 2µs
Operating Temperature	-40°C ~ 100°C
Package / Case	6-DIP (0.400", 10.16mm)
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution logic for the 4N25TM is based on the following critical parameters that must be maintained or exceeded:

Isolation Voltage: Minimum 7500Vpk required for direct substitution
Number of Channels: Single channel configuration mandatory
Output Type: Transistor with base output required
Package Form Factor: 6-DIP through-hole mounting required
Current Transfer Ratio: Minimum 20% @ 10mA
Output Voltage Rating: 30V maximum output voltage
Forward Voltage & Current: Vf 1.18V typical, If 60mA maximum
Switching Speed: 2µs turn-on/turn-off time

The substitute parts identified below meet these core electrical and mechanical requirements. However, variations in isolation voltage specification method (Vpk vs Vrms) and package pitch dimensions must be evaluated for specific application requirements.

Parameter Comparison

Parameter	4N25TM (onsemi)	4N25TVM (Fairchild)	4N25G (Isocom)	4N25M (onsemi)
Product Status	Obsolete	Active	Active	Active
Number of Channels	1	1	1	1
Voltage - Isolation	7500Vpk	4170Vrms	7.5Vpk	4170Vrms
Current Transfer Ratio (Min)	20% @ 10mA	20% @ 10mA	20% @ 10mA	20% @ 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	1.18V	1.2V	1.18V
Current - DC Forward (If) (Max)	60 mA	60 mA	60 mA	60 mA
Vce Saturation (Max)	500mV	500mV	500mV	500mV
Turn On / Turn Off Time (Typ)	2µs, 2µs	2µs, 2µs	Not specified	2µs, 2µs
Operating Temperature	-40°C ~ 100°C	-40°C ~ 100°C	-55°C ~ 100°C	-40°C ~ 100°C
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)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole

Engineering Selection Recommendations

4N25TVM (Fairchild Semiconductor): Active product status with equivalent electrical characteristics to 4N25TM. Isolation voltage specified as 4170Vrms, which is lower than the 7500Vpk rating of the original part. Identical package pitch (0.400", 10.16mm) ensures direct PCB compatibility. Suitable for applications where the lower isolation voltage meets system requirements.

4N25G (Isocom Components 2004 LTD): Active product with ROHS3 compliance. Isolation voltage specified as 7.5Vpk, significantly lower than the 4N25TM requirement. Extended operating temperature range (-55°C ~ 100°C) provides broader thermal coverage. Package pitch matches original (0.400", 10.16mm). Not recommended as a direct substitute due to insufficient isolation voltage specification.

4N25M (onsemi): Active product from the original manufacturer. Isolation voltage specified as 4170Vrms, lower than 4N25TM. Critical difference: package pitch is 0.300" (7.62mm) versus the original 0.400" (10.16mm), requiring PCB layout modification. Electrical characteristics otherwise match the original part. Suitable for redesign scenarios where PCB layout adjustment is acceptable.

Frequently Asked Questions (FAQ)

Q: Can 4N25TVM be used as a direct replacement for 4N25TM?

A: 4N25TVM maintains identical electrical characteristics and package pitch (0.400", 10.16mm), enabling direct PCB substitution. However, the isolation voltage is specified as 4170Vrms compared to 7500Vpk in the original part. Substitution is valid only if system isolation requirements do not exceed 4170Vrms.

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

A: Vpk (peak voltage) and Vrms (root mean square voltage) represent different measurement methods for isolation voltage. Direct comparison requires conversion or reference to component datasheets. The 4N25TM specifies 7500Vpk, while 4N25TVM and 4N25M specify 4170Vrms. These values are not directly equivalent and must be evaluated against specific application isolation requirements.

Q: Why does 4N25M have a different package pitch?

A: The 4N25M uses a 0.300" (7.62mm) pitch 6-DIP package, compared to the 0.400" (10.16mm) pitch of the original 4N25TM. This difference requires PCB layout modification and cannot be used as a direct drop-in replacement without board redesign.

Q: Is 4N25G suitable for high-isolation applications?

A: The 4N25G specifies 7.5Vpk isolation voltage, which is substantially lower than the 4N25TM requirement of 7500Vpk. This part is not suitable for applications requiring the original isolation voltage specification.

Q: What compliance certifications should I verify for substitute parts?

A: 4N25G carries ROHS3 compliance certification. All parts listed carry REACH Unaffected status and EAR99 ECCN classification. Verify compliance requirements against your specific application and regional regulations before final part selection.

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