4N27FR2M Equivalent & Substitute Parts

Part Overview

The 4N27FR2M is an optoisolator transistor with base output manufactured by onsemi, designed for high-voltage isolation applications. This component features a 7500Vpk isolation rating and single-channel transistor output configuration in a 6-SMD surface mount package. The part is currently classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and new design implementations.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N27FR2M
Manufacturer	onsemi
Category	Optoisolators
Number of Channels	1
Voltage - Isolation	7500Vpk
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	Surface Mount
Package / Case	6-SMD, Gull Wing
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the 4N27FR2M is determined by the following critical parameters:

Single-channel configuration: All substitutes must maintain 1-channel optoisolator architecture
Transistor with base output: Output stage must include base connection for external control
Isolation voltage: Minimum 4170Vrms (equivalent to 5900Vpk) acceptable; 7500Vpk primary specification
Current transfer ratio: Minimum 10% @ 10mA maintained across all alternatives
Vce saturation: Maximum 500mV specification consistent across candidates
Input type: DC input required
Operating temperature range: Minimum -40°C to 100°C acceptable; -55°C to 100°C preferred
Package compatibility: Surface mount 6-SMD preferred; through-hole 6-DIP acceptable with mechanical redesign

The 4N27SR2M and 4N27 meet these substitution criteria with documented electrical equivalence and maintained functional performance.

Parameter Comparison

Parameter	4N27FR2M (onsemi)	4N27SR2M (Fairchild)	4N27 (Texas Instruments)
Voltage - Isolation	7500Vpk	4170Vrms	5000Vrms
Number of Channels	1	1	1
Current Transfer Ratio (Min)	10% @ 10mA	10% @ 10mA	10% @ 10mA
Output Type	Transistor with Base	Transistor with Base	Transistor with Base
Voltage - Output (Max)	30V	30V	70V
Vce Saturation (Max)	500mV	500mV	500mV
Voltage - Forward (Vf) (Typ)	1.18V	1.18V	1.3V
Current - DC Forward (If) (Max)	60mA	60mA	60mA
Operating Temperature	-55°C ~ 100°C	-40°C ~ 100°C	-55°C ~ 100°C
Mounting Type	Surface Mount	Surface Mount	Through Hole
Package / Case	6-SMD, Gull Wing	6-SMD, Gull Wing	6-DIP (0.300", 7.62mm)
Product Status	Obsolete	Active	Active

Engineering Selection Recommendations

4N27SR2M (Fairchild Semiconductor): This substitute maintains identical surface mount 6-SMD packaging and electrical characteristics with the exception of reduced isolation voltage (4170Vrms vs. 7500Vpk). Selection is appropriate for applications where the lower isolation specification remains within system requirements. Product status is active with established supply availability.

4N27 (Texas Instruments): This substitute provides equivalent electrical performance with higher maximum output voltage (70V vs. 30V) and maintains the full operating temperature range (-55°C to 100°C). The primary design consideration is the through-hole 6-DIP package, which requires PCB layout modification from the original surface mount configuration. Product status is active with high inventory availability.

Selection between substitutes depends on isolation voltage requirements and PCB assembly capability. The 4N27SR2M provides direct package compatibility; the 4N27 requires mechanical redesign but offers superior output voltage capability.

Frequently Asked Questions (FAQ)

Q: Can the 4N27SR2M directly replace the 4N27FR2M without PCB modification?

A: Yes. The 4N27SR2M maintains identical 6-SMD surface mount packaging and pinout. The primary electrical difference is reduced isolation voltage (4170Vrms vs. 7500Vpk). Substitution is valid if system isolation requirements do not exceed 4170Vrms.

Q: What are the key differences between the 4N27 and 4N27FR2M?

A: The 4N27 uses through-hole 6-DIP packaging instead of surface mount 6-SMD, requiring PCB redesign. The 4N27 provides higher maximum output voltage (70V vs. 30V) and maintains full temperature range compatibility (-55°C to 100°C). Isolation voltage is 5000Vrms, lower than the original 7500Vpk specification.

Q: Is the 4N27 suitable for new surface mount designs?

A: No. The 4N27 is a through-hole component and is not suitable for surface mount assembly processes. For new surface mount designs, the 4N27SR2M is the appropriate selection.

Q: What is the minimum isolation voltage acceptable for substitution?

A: All substitute parts maintain minimum 4170Vrms isolation voltage. Selection must confirm that system isolation requirements do not exceed this specification.

Q: Are there temperature range limitations with the 4N27SR2M?

A: The 4N27SR2M operates from -40°C to 100°C, compared to the original -55°C to 100°C range. Applications requiring operation below -40°C must use the 4N27 (Texas Instruments) or maintain the original 4N27FR2M specification.

Q: Do all substitutes maintain the same current transfer ratio?

A: Yes. All listed substitutes maintain the minimum 10% current transfer ratio @ 10mA specification, ensuring equivalent optical coupling efficiency.

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