4N27S Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N27S is an optoisolator transistor with base output manufactured by onsemi, rated for 5300Vrms isolation voltage in a 6-SMD surface mount package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The 4N27S provides single-channel DC input optoisolation with transistor output including base connection, suitable for applications requiring galvanic isolation in low-voltage control circuits. The obsolete status necessitates identification of active alternative components that maintain functional compatibility.

Key Parameters

Parameter	4N27S Value
Manufacturer	onsemi
Category	Optoisolators
Product Status	Obsolete
Number of Channels	1
Voltage - Isolation	5300Vrms
Current Transfer Ratio (Min)	10% @ 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)	500mV
Operating Temperature	-55°C ~ 100°C
Mounting Type	Surface Mount
Package / Case	6-SMD, Gull Wing
Turn On / Turn Off Time (Typ)	2µs, 2µs
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the 4N27S is determined by the following critical parameters:

Isolation Voltage: Minimum 5000Vrms to maintain equivalent isolation performance
Output Configuration: Transistor with base output required for circuit compatibility
Package Type: 6-SMD, Gull Wing surface mount for PCB compatibility
Current Transfer Ratio: Minimum 10% @ 10mA for functional equivalence
Output Voltage Rating: Minimum 30V to support existing circuit requirements
Operating Temperature Range: Must support -55°C ~ 100°C or equivalent
Input Type: DC input required
Vce Saturation: 500mV maximum for switching performance

Substitute parts are grouped into two categories:

Direct Manufacturer Substitutes (onsemi): Parts from the original manufacturer offering active product status with maintained electrical specifications.

Cross-Manufacturer Alternatives (Vishay, Lite-On, Isocom): Parts from alternative manufacturers meeting the isolation voltage, package, and output configuration requirements. These parts maintain functional compatibility while offering different availability and compliance profiles.

Parameter Comparison

Parameter	4N27S (Main)	4N27SM	4N27-X007	4N27-X009T	4N27-X017T	4N27XSM
Manufacturer	onsemi	onsemi	Vishay	Vishay	Vishay	Isocom
Product Status	Obsolete	Active	Active	Active	Active	Active
Voltage - Isolation	5300Vrms	4170Vrms	5000Vrms	5000Vrms	5000Vrms	5300Vrms
Number of Channels	1	1	1	1	1	1
Current Transfer Ratio (Min)	10% @ 10mA	10% @ 10mA	10% @ 10mA	10% @ 10mA	10% @ 10mA	10% @ 10mA
Output Type	Transistor with Base	Transistor with Base	Transistor with Base	Transistor with Base	Transistor with Base	Transistor with Base
Voltage - Output (Max)	30V	30V	70V	70V	70V	30V
Current - DC Forward (If) (Max)	100 mA	60 mA	60 mA	60 mA	60 mA	60 mA
Voltage - Forward (Vf) (Typ)	1.18V	1.18V	1.36V	1.36V	1.36V	1.2V
Vce Saturation (Max)	500mV	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	-55°C ~ 100°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	6-SMD, Gull Wing	6-SMD, Gull Wing	6-SMD, Gull Wing	6-SMD, Gull Wing	6-SMD, Gull Wing	6-SMD, Gull Wing
Turn On / Turn Off Time (Typ)	2µs, 2µs	2µs, 2µs	Not specified	Not specified	Not specified	Not specified
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: 4N27XSM (Isocom Components)

The 4N27XSM provides the closest electrical match to the 4N27S with identical isolation voltage (5300Vrms), matching output voltage rating (30V), and equivalent operating temperature range (-55°C ~ 100°C). This part is active and ROHS3 compliant. The 6-SMD Gull Wing package ensures direct PCB compatibility. Forward current specification (60 mA) is lower than the original 100 mA, requiring circuit verification for applications at maximum input current levels.

Secondary Recommendation: 4N27-X009T or 4N27-X017T (Vishay)

Both Vishay parts maintain 5000Vrms isolation voltage, meeting the minimum isolation requirement. These parts are active with ROHS3 compliance and support the full -55°C ~ 100°C temperature range. The higher output voltage rating (70V) provides additional design margin. These parts are available in Tape & Reel packaging with higher inventory levels. Forward current specification (60 mA) requires circuit verification.

Alternative: 4N27SM (onsemi)

The 4N27SM is an active onsemi product maintaining the same manufacturer lineage as the obsolete 4N27S. However, the reduced isolation voltage (4170Vrms) falls below the 5000Vrms minimum threshold and the narrower operating temperature range (-40°C ~ 100°C) may not support all applications. This part is suitable only for applications with lower isolation voltage requirements.

Not Recommended: 4N27S-TA and 4N27S-TA1 (Lite-On)

The Lite-On variants specify 1500Vrms isolation voltage, significantly below the 5300Vrms rating of the original part. These are not suitable substitutes for applications requiring the original isolation specification.

Frequently Asked Questions (FAQ)

Q: Can 4N27SM replace 4N27S directly?

A: 4N27SM is not a direct replacement. While both are onsemi products with identical package and output configuration, the 4N27SM isolation voltage (4170Vrms) is lower than the 4N27S specification (5300Vrms). Use only if your application isolation requirement is 4170Vrms or lower. The operating temperature range is also narrower (-40°C vs -55°C minimum).

Q: What is the minimum isolation voltage for substitution?

A: Substitutes must maintain at least 5000Vrms isolation voltage to meet the functional requirements of the 4N27S. Parts with lower isolation ratings (such as 4N27SM at 4170Vrms) are not equivalent.

Q: Are Vishay 4N27-X007, 4N27-X009T, and 4N27-X017T interchangeable?

A: Yes, these three Vishay parts are electrically equivalent. The primary difference is packaging: 4N27-X007 is supplied in Tube, while 4N27-X009T and 4N27-X017T are supplied in Tape & Reel. Select based on your procurement and assembly requirements.

Q: Does the forward current difference affect substitution?

A: The 4N27S specifies 100 mA maximum forward current, while most substitutes specify 60 mA. If your circuit operates the LED input at currents above 60 mA, verify the substitute part's performance at your actual operating current. For standard applications operating at 10-20 mA input current, this difference is not critical.

Q: What is the impact of the higher output voltage rating on Vishay parts?

A: Vishay 4N27-X007, 4N27-X009T, and 4N27-X017T specify 70V maximum output voltage compared to 30V on the 4N27S. This higher rating provides additional design margin and does not negatively impact substitution. Existing circuits designed for 30V output will operate within the Vishay parts' specifications.

Q: Are all substitute parts ROHS3 compliant?

A: All active substitute parts listed (4N27SM, 4N27-X007, 4N27-X009T, 4N27-X017T, 4N27XSM) are ROHS3 compliant. The original 4N27S does not specify RoHS status.

Q: Can I use 4N27SMT&R as a substitute?

A: 4N27SMT&R is not recommended. This Isocom part specifies 7.5Vpk isolation voltage, which is significantly below the 5300Vrms requirement and indicates a different product specification. This part is not functionally equivalent.

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