BD679AG Equivalent & Substitute Parts

Part Overview

The BD679AG is an NPN Darlington bipolar junction transistor manufactured by onsemi, rated for 80 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-126 through-hole package. This device is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design support and procurement continuity. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives with modified parameters suitable for the same application categories.

Substiute Parts

BD679AG

onsemiIn Stock: 1413BD679AG Datasheet

Current PartRFQ

BD679AS

onsemiIn Stock: 1998BD679AS Datasheet

DirectRFQ

BD681G

onsemiIn Stock: 20339BD681G Datasheet

DirectRFQ

BD679A

STMicroelectronicsIn Stock: 1566BD679A Datasheet

DirectRFQ

BD679

STMicroelectronicsIn Stock: 23392BD679 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD679AG is determined by equivalence in the following critical parameters: transistor type (NPN Darlington), maximum collector current (4 A), maximum collector-emitter breakdown voltage (80 V or higher), maximum power dissipation (40 W), and through-hole mounting configuration. Parts are grouped into three categories based on substitution relationship:

Direct Equivalents maintain all electrical specifications and differ only in packaging format or supplier device package designation. These parts are interchangeable in identical PCB layouts.

Voltage-Rated Upgrades provide higher collector-emitter breakdown voltage (100 V) while maintaining all other electrical parameters. These parts are suitable for applications where the original 80 V rating is marginal or where design margin improvement is required.

Manufacturer Variants represent the same base part number from alternative manufacturers or with modified saturation characteristics, maintaining core electrical performance within specified tolerances.

Parameter Comparison

Engineering Selection Recommendations

BD679AS (onsemi) is the primary direct equivalent for BD679AG replacement. This part maintains identical electrical specifications and is currently in active product status with 1956 units in stock. The BD679AS differs only in supplier device package designation (TO-126-3 versus TO-126) and packaging format (Bulk versus original specification). This part is suitable for direct substitution in existing designs without circuit modification.

BD681G (onsemi) serves as a voltage-rated upgrade option. With a 100 V collector-emitter breakdown voltage compared to the BD679AG's 80 V rating, this part provides enhanced voltage margin while maintaining 4 A collector current and 40 W power dissipation. The BD681G exhibits modified saturation characteristics (2.5V @ 30mA, 1.5A versus 2.8V @ 40mA, 2A) and altered DC current gain test conditions (750 @ 1.5A, 3V versus 750 @ 2A, 3V). This part is appropriate for applications requiring higher voltage headroom. The BD681G is in active status with 20300 units in stock.

BD679A (STMicroelectronics) provides equivalent electrical performance with alternative packaging in SOT-32-3 format. This part maintains the 80 V voltage rating and 4 A current specification. The BD679A is in active product status with 1475 units in stock. Selection of this part requires PCB layout modification to accommodate the SOT-32-3 package geometry.

BD679 (STMicroelectronics) represents an upgrade variant with modified saturation characteristics and DC current gain test conditions identical to BD681G, while maintaining the 80 V voltage rating of the original BD679AG. This part is packaged in SOT-32-3 format and is in active status with 23300 units in stock. Like BD679A, this part requires PCB layout modification.

All substitute parts maintain ROHS3 compliance and REACH unaffected status consistent with the original BD679AG specification.

Frequently Asked Questions (FAQ)

Q: Can BD679AS be used as a direct replacement for BD679AG in existing PCB designs?

A: Yes. BD679AS maintains identical electrical specifications and through-hole mounting configuration. The difference in supplier device package designation (TO-126-3 versus TO-126) does not affect electrical performance or pin compatibility. PCB layout modification is not required.

Q: What is the primary advantage of selecting BD681G over BD679AS?

A: BD681G provides a 100 V collector-emitter breakdown voltage rating compared to 80 V for BD679AS. This higher voltage rating offers increased design margin in applications where supply voltage or transient overvoltage conditions approach the 80 V limit. All other electrical parameters remain equivalent at the specified test conditions.

Q: Are the STMicroelectronics BD679 and BD679A parts pin-compatible with the onsemi BD679AG?

A: Both STMicroelectronics parts use SOT-32-3 package format, which differs from the TO-126 package of BD679AG. While pin configuration is identical, the physical package geometry requires PCB layout modification. Direct socket substitution is not possible without adapter hardware.

Q: What is the difference between BD679A and BD679 from STMicroelectronics?

A: Both parts are packaged in SOT-32-3 format and maintain the 80 V voltage rating. The BD679 exhibits modified saturation characteristics (2.5V @ 30mA, 1.5A) and DC current gain test conditions (750 @ 1.5A, 3V) compared to BD679A (2.8V @ 40mA, 2A and 750 @ 2A, 3V). These differences reflect measurement conditions rather than fundamental performance changes. Both parts are suitable for equivalent applications.

Q: Why is the BD679AG classified as obsolete?

A: The BD679AG is no longer in active production. Equivalent and substitute parts in active status (BD679AS, BD681G, BD679A, and BD679) are available for new designs and replacement procurement.

Q: Does operating temperature range affect part selection?

A: BD679AG specifies -55°C to 150°C operating range. BD679AS, BD679A, and BD679 specify 150°C maximum without lower temperature limit documentation. BD681G maintains the full -55°C to 150°C range. For applications requiring operation below 0°C, BD679AG or BD681G are appropriate selections.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. BD679AS, BD681G, BD679A, and BD679 are all ROHS3 compliant and REACH unaffected, consistent with the original BD679AG specification.