4N27 Optoisolator Transistor with Base Output

Part Overview

The 4N27 is a 6-DIP optoisolator with transistor output and integrated base connection, designed for high-voltage isolation applications. Manufactured by onsemi, this component provides 5300Vrms isolation with a single channel configuration suitable for DC input switching and signal isolation in industrial and consumer electronics.

The 4N27 is classified as obsolete, necessitating identification of equivalent and substitute parts for new designs and ongoing production requirements. Alternative models from active product lines offer comparable electrical characteristics while maintaining package compatibility.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N27
Manufacturer	onsemi
Category	Optoisolators
Package / Case	6-DIP (0.300", 7.62mm)
Number of Channels	1
Voltage - Isolation	5300Vrms
Current Transfer Ratio (Min)	10% @ 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 4N27 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
Isolation voltage rating: minimum 2500Vrms
Current transfer ratio: minimum 10% @ 10mA
Vce saturation: 500mV maximum
Operating temperature range: -55°C to 100°C minimum
Mounting type: Through Hole

Substitute parts must maintain electrical and mechanical compatibility across these parameters to ensure direct replacement capability in existing circuit designs.

Parameter Comparison

Parameter	4N27 (onsemi)	4N27M (onsemi)	4N25-000E (Broadcom)	4N27 (Texas Instruments)	4N27-X000 (Vishay)
Voltage - Isolation	5300Vrms	4170Vrms	2500Vrms	5000Vrms	5000Vrms
Current Transfer Ratio (Min)	10% @ 10mA	10% @ 10mA	20% @ 10mA	10% @ 10mA	10% @ 10mA
Voltage - Output (Max)	30V	30V	30V	70V	70V
Current - Output / Channel	Not specified	Not specified	100mA	50mA	50mA
Current - DC Forward (If) (Max)	100mA	60mA	80mA	60mA	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
Package / Case	6-DIP (0.300", 7.62mm)	6-DIP (0.300", 7.62mm)	6-DIP (0.300", 7.62mm)	6-DIP (0.300", 7.62mm)	6-DIP (0.300", 7.62mm)
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Replacement (Active Product Status):

The 4N27M from onsemi provides the closest electrical match with active product status and ROHS3 compliance. This part maintains the same current transfer ratio, Vce saturation, and package configuration. The reduced isolation voltage (4170Vrms vs. 5300Vrms) and narrower operating temperature range (-40°C to 100°C vs. -55°C to 100°C) require circuit-level evaluation for applications demanding the original specifications.

The 4N27-X000 from Vishay Semiconductor Opto Division offers 5000Vrms isolation with ROHS3 compliance and active product status. This part supports higher output voltage (70V vs. 30V) and maintains the full -55°C to 100°C operating range, making it suitable for designs requiring maximum isolation voltage retention.

Alternative Selection (Lower Isolation Voltage):

The 4N25-000E from Broadcom Limited provides active product status with ROHS3 compliance but operates at 2500Vrms isolation. This part features higher current transfer ratio (20% @ 10mA) and specified output current (100mA). Selection requires confirmation that reduced isolation voltage meets application requirements.

Compliance Considerations:

Texas Instruments 4N27 variants are RoHS non-compliant and REACH-affected, limiting suitability for new designs subject to environmental regulations. These parts maintain 5000Vrms isolation and full temperature range but do not meet modern compliance standards.

Frequently Asked Questions (FAQ)

Q: Can the 4N27M directly replace the obsolete 4N27?

A: The 4N27M maintains package compatibility and core electrical characteristics (current transfer ratio, Vce saturation, output type). However, the reduced isolation voltage (4170Vrms vs. 5300Vrms) and narrower operating temperature minimum (-40°C vs. -55°C) require circuit validation. Applications operating at the temperature extremes or requiring maximum isolation voltage must evaluate alternative parts.

Q: What is the primary difference between 4N27-X000 and 4N27M?

A: The 4N27-X000 maintains higher isolation voltage (5000Vrms) and supports higher output voltage (70V vs. 30V), while the 4N27M offers lower isolation voltage (4170Vrms) with 30V output maximum. Both maintain the same current transfer ratio and Vce saturation specifications. Selection depends on circuit voltage requirements.

Q: Is the 4N25-000E suitable for applications requiring 5300Vrms isolation?

A: No. The 4N25-000E operates at 2500Vrms isolation, significantly below the original 4N27 specification. This part is suitable only for applications where reduced isolation voltage is acceptable. The higher current transfer ratio (20% vs. 10%) and specified output current (100mA) may provide design advantages in lower-voltage isolation circuits.

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 configuration, ensuring mechanical compatibility with existing PCB layouts and through-hole assembly processes.

Q: Which substitute part offers the best compliance profile?

A: The 4N27M, 4N25-000E, and 4N27-X000 all carry ROHS3 compliance. The 4N27M and 4N27-X000 are from manufacturers with active product status and full compliance certifications, making them preferred for new designs subject to environmental regulations.

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