4N25 Optoisolator Transistor with Base Output

Part Overview

The 4N25 is a single-channel optoisolator with transistor output and integrated base connection, designed for galvanic isolation in DC-coupled applications. Manufactured by onsemi, this 6-DIP through-hole component provides 5300Vrms isolation voltage and is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and ongoing production requirements.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N25
Manufacturer	onsemi
Category	Optoisolators
Package / Case	6-DIP (0.300", 7.62mm)
Number of Channels	1
Voltage - Isolation	5300Vrms
Current Transfer Ratio (Min)	20% @ 10mA
Output Type	Transistor with Base
Voltage - Output (Max)	30V
Vce Saturation (Max)	500mV
Operating Temperature	-55°C ~ 100°C
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the 4N25 is determined by the following critical parameters:

Package compatibility: 6-DIP (0.300", 7.62mm) form factor
Output configuration: Transistor with Base
Input type: DC
Number of channels: 1
Isolation voltage: minimum 2500Vrms
Current transfer ratio: minimum 20% @ 10mA
Vce saturation: 500mV maximum
Operating temperature range: -55°C to 100°C minimum

Parts meeting these criteria are classified as direct or similar substitutes. Direct substitutes maintain electrical equivalence across all specified parameters. Similar substitutes meet functional requirements but may have minor parameter variations that do not affect circuit operation within the defined application envelope.

Parameter Comparison

Parameter	4N25 (onsemi)	4N25M (onsemi)	4N25 (Texas Instruments)	4N25-000E (Broadcom)	4N25-X000 (Vishay)
Voltage - Isolation	5300Vrms	4170Vrms	5000Vrms	2500Vrms	5000Vrms
Current Transfer Ratio (Min)	20% @ 10mA	20% @ 10mA	20% @ 10mA	20% @ 10mA	20% @ 10mA
Voltage - Output (Max)	30V	30V	70V	30V	70V
Current - DC Forward (If) (Max)	100mA	60mA	60mA	80mA	60mA
Vce Saturation (Max)	500mV	500mV	500mV	500mV	500mV
Operating Temperature	-55°C ~ 100°C	-40°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 100°C
Turn On / Turn Off Time (Typ)	2µs, 2µs	2µs, 2µs	—	—	—
Rise / Fall Time (Typ)	—	—	2µs, 2µs	3µs, 3µs	2µs, 2µs
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	—	ROHS3 Compliant	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

4N25M (onsemi) — Active product with ROHS3 compliance. Isolation voltage reduced to 4170Vrms and forward current limited to 60mA. Suitable for applications where the lower isolation voltage and reduced input current are acceptable. Operating temperature minimum raised to -40°C; verify compatibility with designs requiring -55°C operation.

4N25 (Texas Instruments) — Active product with 5000Vrms isolation voltage matching the original specification. Output voltage rating increased to 70V with 50mA output current capability. RoHS non-compliant; REACH affected. Electrical performance equivalent for standard applications.

4N25-X000 (Vishay Semiconductor Opto Division) — Active product with 5000Vrms isolation voltage and ROHS3 compliance. Output voltage rating increased to 70V with 50mA output current capability. Timing characteristics match the original specification (2µs rise/fall time).

4N25-000E (Broadcom Limited) — Active product with ROHS3 compliance. Isolation voltage reduced to 2500Vrms; use only in applications where lower isolation voltage is acceptable. Rise/fall time increased to 3µs; verify timing compatibility. Forward current increased to 80mA.

Frequently Asked Questions (FAQ)

Q: Can I use 4N25M as a direct replacement for the original 4N25?

A: 4N25M is functionally compatible for most applications. The isolation voltage is reduced from 5300Vrms to 4170Vrms, and the maximum forward current is limited to 60mA versus 100mA. Verify that your circuit design does not require the higher isolation voltage or input current capability. The operating temperature minimum is -40°C instead of -55°C.

Q: What is the difference between the Texas Instruments 4N25 and the Vishay 4N25-X000?

A: Both provide 5000Vrms isolation voltage and 2µs timing characteristics. The Texas Instruments version is RoHS non-compliant and REACH affected, while the Vishay version is ROHS3 compliant. Both support 70V output voltage and 50mA output current. Select based on compliance requirements for your application.

Q: Is the 4N25-000E (Broadcom) suitable for high-isolation applications?

A: The 4N25-000E provides 2500Vrms isolation, which is significantly lower than the original 4N25 (5300Vrms). Use this part only in applications where the lower isolation voltage meets the design requirements. It is not suitable as a general replacement for designs requiring 5000Vrms or higher isolation.

Q: Are all substitute parts available in the same 6-DIP package?

A: Yes. All listed substitute parts use the 6-DIP (0.300", 7.62mm) package and are compatible with through-hole PCB layouts designed for the original 4N25.

Q: Which substitute part has the best compliance status?

A: 4N25M, 4N25-X000, and 4N25-000E are all ROHS3 compliant. The Texas Instruments 4N25 is RoHS non-compliant. For new designs requiring RoHS compliance, select from the ROHS3-compliant options.

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