6N138 Optoisolator Equivalent & Substitute Parts

Part Overview

The 6N138 is a single-channel optoisolator with Darlington output and base connection, designed for high-voltage isolation applications. Manufactured by Broadcom Limited, this component provides 3750Vrms isolation with a current transfer ratio range of 300% to 2600% at 1.6mA input current. The part is currently active in production and widely used in industrial control, power supply, and signal isolation circuits. Substitute parts may be required due to inventory availability, packaging preferences, compliance requirements, or manufacturer discontinuation of specific variants.

Substiute Parts

6N138

Broadcom LimitedIn Stock: 121846N138 Datasheet

Current PartRFQ

6N138-000E

Broadcom LimitedIn Stock: 18296N138-000E Datasheet

Parametric EquivalentRFQ

6N138M

Fairchild SemiconductorIn Stock: 155116N138M Datasheet

DirectRFQ

6N138

Fairchild SemiconductorIn Stock: 121646N138 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 6N138 are classified based on electrical parameter compatibility and mechanical interchangeability. The primary substitution criteria are:

• Isolation Voltage: Minimum 3750Vrms required for direct substitution
• Output Configuration: Must be Darlington with Base output
• Current Transfer Ratio: Minimum 300% @ 1.6mA
• Package Compatibility: 8-DIP form factor with 0.300" or 0.400" pitch
• Output Specifications: Maximum output voltage 7V, output current 60mA per channel
• Input Type: DC input required
• Operating Temperature: Must support -40°C to 85°C minimum range

The 6N138-000E is a parametric equivalent manufactured by Broadcom Limited with identical electrical specifications and RoHS3 compliance. The 6N138M from Fairchild Semiconductor provides enhanced isolation voltage (5000Vrms) with compatible electrical parameters but different packaging pitch. The legacy 6N138 from Fairchild Semiconductor is marked obsolete and included for reference only.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute: 6N138-000E (Broadcom Limited)

The 6N138-000E is the recommended direct substitute for the 6N138. Both parts are manufactured by Broadcom Limited with identical electrical specifications, package dimensions, and pin configuration. The 6N138-000E offers the additional advantage of RoHS3 compliance, making it suitable for applications requiring environmental and regulatory adherence. Both parts are currently in active production with stable inventory availability.

Alternative Substitute: 6N138M (Fairchild Semiconductor)

The 6N138M provides enhanced isolation voltage (5000Vrms versus 3750Vrms) while maintaining all critical electrical parameters including current transfer ratio, output voltage, and output current specifications. The 6N138M is suitable for applications requiring higher isolation margins. However, the package pitch differs (0.400" versus 0.300"), requiring PCB layout verification before substitution. The 6N138M is supplied in bulk packaging rather than tube format.

Obsolete Reference: 6N138 (Fairchild Semiconductor)

The Fairchild Semiconductor 6N138 is marked as obsolete and should not be selected for new designs. This part is included for reference only when identifying legacy component equivalents in existing systems.

Frequently Asked Questions (FAQ)

Q: Can the 6N138-000E be used as a direct replacement for the 6N138?

A: Yes. The 6N138-000E is electrically and mechanically identical to the 6N138 (Broadcom). Both parts share the same isolation voltage (3750Vrms), current transfer ratio range (300% to 2600%), output specifications, and 8-DIP package with 0.300" pitch. The 6N138-000E additionally provides RoHS3 compliance.

Q: What is the difference between the 6N138 and 6N138M?

A: The primary difference is isolation voltage: the 6N138M provides 5000Vrms isolation compared to 3750Vrms for the 6N138. The 6N138M also features slightly faster switching times (1.4µs turn-on versus 1.6µs). The package pitch differs (0.400" for 6N138M versus 0.300" for 6N138), which may affect PCB compatibility. Both parts maintain identical output current (60mA) and output voltage (7V) specifications.

Q: Is the package pitch difference between 6N138 and 6N138M critical?

A: Yes. The 6N138 uses 0.300" (7.62mm) pitch while the 6N138M uses 0.400" (10.16mm) pitch. These dimensions are not interchangeable on standard PCBs. Verify PCB footprint compatibility before selecting the 6N138M as a substitute.

Q: Can the obsolete Fairchild 6N138 be used in new designs?

A: No. The Fairchild 6N138 is marked obsolete and should not be selected for new designs. Use the active Broadcom 6N138 or 6N138-000E instead.

Q: What are the RoHS compliance differences?

A: The 6N138-000E is RoHS3 compliant, while the original 6N138 (Broadcom) is RoHS non-compliant. For applications requiring environmental compliance certification, the 6N138-000E is the appropriate selection.

Q: Are all substitute parts rated for the same operating temperature range?

A: The 6N138 and 6N138-000E are rated -40°C to 85°C. The 6N138M maintains the same -40°C to 85°C range. The obsolete Fairchild 6N138 has a wider range (-55°C to 100°C) but should not be used due to obsolescence.