BU508AFTBTU Equivalent & Substitute Parts

Part Overview

The BU508AFTBTU is an NPN bipolar junction transistor manufactured by onsemi, rated for 700 V collector-emitter breakdown voltage and 5 A maximum collector current in a TO-3P-3 Full Pack through-hole package. This device is classified as obsolete product status. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this transistor topology.

Substiute Parts

BU508AFTBTU

onsemiIn Stock: 813BU508AFTBTU Datasheet

Current PartRFQ

BU508AW

STMicroelectronicsIn Stock: 15866BU508AW Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BU508AFTBTU is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

• Transistor type must be NPN
• Voltage - Collector Emitter Breakdown (Max) must be 700 V or greater
• Current - Collector (Ic) (Max) must be 5 A or greater
• Operating temperature rating must support 150°C (TJ) or higher
• Vce saturation characteristics must be compatible with application requirements

Mechanical Compatibility Criteria:

• Mounting type must be Through Hole
• Package must accommodate TO-3P-3 or equivalent footprint dimensions

The BU508AW substitute part meets these criteria with enhanced electrical performance characteristics while maintaining the same voltage rating and exceeding the current rating specification.

Parameter Comparison

Engineering Selection Recommendations

BU508AW Substitution Assessment:

The BU508AW from STMicroelectronics is a direct functional substitute for the BU508AFTBTU. Both devices share identical voltage ratings (700 V) and meet or exceed the current requirements (8 A versus 5 A). The BU508AW provides superior power dissipation capability (125 W versus 60 W) and improved DC current gain characteristics.

Product Status Consideration:

The BU508AFTBTU is classified as obsolete, while the BU508AW maintains active product status with ROHS3 compliance certification. This status differential supports long-term supply chain viability and regulatory alignment for new designs or production continuations.

Package Transition:

The primary design consideration involves package transition from TO-3P-3 Full Pack to TO-247-3. Both packages are through-hole mounting types with different physical footprints. PCB layout modification is required to accommodate the TO-247-3 package geometry.

Compliance and Certifications:

Both parts maintain REACH Unaffected status and EAR99 ECCN classification. The BU508AW provides additional ROHS3 compliance certification, supporting regulatory requirements in restricted substance applications.

Frequently Asked Questions (FAQ)

Q: Can the BU508AW directly replace the BU508AFTBTU without circuit modification?

A: Electrical substitution is valid based on voltage and current ratings. However, package geometry differs between TO-3P-3 and TO-247-3, requiring PCB footprint redesign. Circuit performance remains compatible when proper thermal management is maintained.

Q: What are the key electrical differences between these parts?

A: The BU508AW provides higher maximum collector current (8 A versus 5 A) and greater power dissipation capability (125 W versus 60 W). DC current gain is improved in the BU508AW. Both maintain identical 700 V breakdown voltage and 150°C operating temperature ratings.

Q: Is the BU508AW suitable for applications originally designed for the BU508AFTBTU?

A: Yes, the BU508AW meets all electrical requirements for applications utilizing the BU508AFTBTU. The enhanced current and power ratings provide design margin. Package footprint modification is the primary implementation consideration.

Q: What is the significance of the product status difference?

A: The BU508AFTBTU is obsolete, indicating discontinued manufacturing and limited availability. The BU508AW is active product, ensuring ongoing supply chain support and manufacturing continuity for production requirements.

Q: Are there thermal management differences between the TO-3P-3 and TO-247-3 packages?

A: Both packages are through-hole mounted with different physical geometries. Thermal performance depends on PCB copper area, heatsink interface, and mounting configuration. Consult package datasheets for specific thermal resistance specifications.

Q: Does the BU508AW require different biasing or drive circuit design?

A: Base electrical biasing principles remain consistent. The improved DC current gain in the BU508AW may allow reduced base drive current for equivalent collector current levels. Circuit validation is necessary for specific application parameters.

Q: What compliance certifications apply to the BU508AW?

A: The BU508AW is ROHS3 compliant and maintains REACH Unaffected status. Both parts share EAR99 ECCN classification and identical HTSUS coding for regulatory and trade purposes.