MOC8108 Equivalent & Substitute Parts

Part Overview

The MOC8108 is a transistor output optoisolator manufactured by onsemi, rated for 5300Vrms isolation voltage in a 6-DIP through-hole package. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The MOC8108 provides single-channel DC input isolation with transistor output capability, suitable for applications requiring high-voltage galvanic isolation.

Substiute Parts

MOC8108

onsemiIn Stock: 1353MOC8108 Datasheet

Current PartRFQ

CNY17F4M

Fairchild SemiconductorIn Stock: 1556CNY17F4M Datasheet

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CNY17-4-000E

Broadcom LimitedIn Stock: 12615CNY17-4-000E Datasheet

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CNY17F-4

Lite-On Inc.In Stock: 45114CNY17F-4 Datasheet

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MOC8108

onsemiIn Stock: 1353MOC8108 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MOC8108 is determined by the following critical parameters:

• Package compatibility: 6-DIP (0.300", 7.62mm) through-hole mounting
• Isolation voltage: Minimum 5000Vrms (MOC8108 specifies 5300Vrms)
• Output configuration: Transistor output topology
• Number of channels: Single channel
• Input type: DC
• Maximum output voltage: 70V
• Operating temperature range: Must support -55°C minimum
• Mounting type: Through hole

The three substitute parts listed below meet these core compatibility criteria while maintaining functional equivalence for typical isolation applications.

Parameter Comparison

Engineering Selection Recommendations

CNY17-4-000E (Broadcom Limited) is the primary substitute for MOC8108 applications. This part maintains 5000Vrms isolation voltage (within 300V of the original specification), supports the full -55°C to 100°C operating range, and is actively manufactured. The CNY17-4-000E features transistor output with base access, enabling enhanced circuit flexibility. Higher output current capability (150mA vs. 50mA) provides design margin for demanding applications. RoHS3 compliance and REACH unaffected status confirm environmental regulatory alignment.

CNY17F-4 (Lite-On Inc.) serves as a secondary substitute with identical isolation voltage (5000Vrms) and operating temperature range to CNY17-4-000E. This part is actively produced with high inventory availability (45,100 pcs). The CNY17F-4 provides standard transistor output without base connection, suitable for applications not requiring base drive control. RoHS3 compliance and REACH unaffected status are confirmed.

CNY17F4M (Fairchild Semiconductor) is a tertiary option with reduced isolation voltage (4170Vrms). This part is suitable only for applications where isolation voltage requirements are less stringent than the original MOC8108 specification. The CNY17F4M operates within -40°C to 100°C range, excluding the -55°C lower temperature extreme. Use this substitute only when isolation voltage and temperature range constraints permit.

Frequently Asked Questions (FAQ)

Q: Can CNY17F4M replace MOC8108 in all applications?

A: No. CNY17F4M has reduced isolation voltage (4170Vrms vs. 5300Vrms) and a narrower operating temperature range (-40°C to 100°C vs. -55°C to 100°C). Use CNY17F4M only when your application does not require the full isolation voltage or extended low-temperature operation of the original MOC8108.

Q: What is the difference between CNY17-4-000E and CNY17F-4?

A: Both parts provide 5000Vrms isolation and -55°C to 100°C operation. The primary difference is output configuration: CNY17-4-000E includes a base connection for transistor output, while CNY17F-4 provides standard transistor output without base access. CNY17-4-000E also supports higher output current (150mA vs. 150mA). Select based on circuit requirements for base drive control.

Q: Are all substitute parts pin-compatible with MOC8108?

A: All substitute parts use the 6-DIP (0.300", 7.62mm) through-hole package. Physical footprint compatibility is confirmed. Verify pinout assignments in device datasheets before PCB layout to ensure correct signal routing, as output configurations differ between parts.

Q: What is the impact of lower current transfer ratio in substitute parts?

A: MOC8108 specifies 250-600% CTR @ 10mA, while substitutes specify 160-320% CTR @ 10mA. Lower CTR requires higher input current to achieve equivalent output switching. Circuit designs must account for increased input LED current requirements when using substitute parts.

Q: Can I use CNY17-4-000E in place of MOC8108 without circuit modifications?

A: Physical and electrical compatibility is confirmed for standard applications. However, the base connection on CNY17-4-000E output provides additional circuit design flexibility not present in MOC8108. Existing circuits will function without modification, but new designs should evaluate base drive control benefits.

Q: Which substitute has the best long-term availability?

A: CNY17F-4 (Lite-On) shows the highest inventory (45,100 pcs) and active product status. CNY17-4-000E (Broadcom) also maintains active status with substantial inventory (12,550 pcs). Both are suitable for production designs requiring long-term component supply assurance.