BD679G Equivalent & Substitute Parts

Part Overview

The BD679G 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 Through Hole TO-126 package. This device is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design support and procurement continuity. The BD679G delivers 40 W maximum power dissipation with a minimum DC current gain of 750 at specified operating conditions, suitable for switching and amplification applications requiring Darlington configuration performance.

Substiute Parts

BD679G

onsemiIn Stock: 1414BD679G Datasheet

Current PartRFQ

BD681G

onsemiIn Stock: 20339BD681G Datasheet

DirectRFQ

BD679AS

onsemiIn Stock: 1998BD679AS Datasheet

UpgradeRFQ

BD679

STMicroelectronicsIn Stock: 23392BD679 Datasheet

DirectRFQ

BD679A

STMicroelectronicsIn Stock: 1566BD679A Datasheet

UpgradeRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD679G is determined by electrical and mechanical compatibility across the following critical parameters: transistor type (NPN - Darlington configuration), maximum collector current (4 A), maximum power dissipation (40 W), DC current gain characteristics (750 minimum), operating temperature range (-55°C to 150°C), and Through Hole mounting compatibility. Substitute parts must maintain these core electrical specifications to ensure functional equivalence in circuit applications.

The substitute parts are grouped into two categories:

Direct Electrical Equivalents: Parts maintaining identical or superior voltage ratings, current ratings, gain characteristics, and saturation voltage specifications within the same thermal operating range.

Voltage-Rated Upgrades: Parts with elevated collector-emitter breakdown voltage ratings (100 V versus 80 V) while maintaining all other electrical parameters, suitable for applications requiring enhanced voltage margin.

Package Variants: Parts available in alternative Through Hole package designations (TO-126-3 and SOT-32-3) with identical electrical performance, accommodating different PCB layout and assembly requirements.

Parameter Comparison

Engineering Selection Recommendations

BD681G (onsemi): This part is an active product with identical electrical characteristics to the BD679G except for an elevated collector-emitter breakdown voltage rating of 100 V versus 80 V. The BD681G maintains 4 A maximum collector current, 40 W power dissipation, 750 minimum DC current gain, and identical saturation voltage specifications. The higher voltage rating provides additional design margin for applications subject to transient overvoltage conditions. The BD681G is packaged in TO-126 configuration, matching the original BD679G footprint. This part is suitable for direct substitution in applications where the 80 V rating is not a limiting constraint.

BD679AS (onsemi): This part is an active product maintaining the 80 V collector-emitter breakdown voltage and 4 A current rating of the BD679G. The BD679AS is supplied in TO-126-3 package configuration and exhibits slightly elevated saturation voltage specifications (2.8 V @ 40 mA, 2 A versus 2.5 V @ 30 mA, 1.5 A). The DC current gain is specified at 2 A collector current rather than 1.5 A. This part is suitable for substitution where TO-126-3 package compatibility is required.

BD679 (STMicroelectronics): This part is an active product from an alternative manufacturer with identical electrical specifications to the BD679G. The BD679 maintains 80 V breakdown voltage, 4 A collector current, 40 W power dissipation, and 750 minimum DC current gain. The part is supplied in SOT-32-3 package configuration. This part is suitable for substitution where STMicroelectronics sourcing is preferred and SOT-32-3 package compatibility is available.

BD679A (STMicroelectronics): This part is an active product from STMicroelectronics with 80 V breakdown voltage and 4 A current rating. The BD679A exhibits saturation voltage specifications of 2.8 V @ 40 mA, 2 A and DC current gain specified at 2 A collector current. The part is supplied in SOT-32-3 package configuration. This part is suitable for substitution where STMicroelectronics sourcing and SOT-32-3 package compatibility are required.

All substitute parts are ROHS3 compliant and REACH unaffected, maintaining regulatory compliance equivalent to the original BD679G.

Frequently Asked Questions (FAQ)

Q: Can the BD681G replace the BD679G in all applications?

A: The BD681G is electrically compatible with the BD679G for applications operating at or below 80 V collector-emitter voltage. The BD681G features a 100 V breakdown voltage rating, providing additional voltage margin. Both parts maintain identical 4 A current rating, 40 W power dissipation, and 750 minimum DC current gain. The TO-126 package footprint is identical. Substitution is valid where the higher voltage rating does not create design conflicts.

Q: What is the difference between BD679AS and BD679G?

A: The BD679AS and BD679G share identical electrical ratings: 80 V breakdown voltage, 4 A collector current, and 40 W power dissipation. The primary differences are product status (BD679AS is active; BD679G is obsolete) and package designation (BD679AS is TO-126-3; BD679G is TO-126). The BD679AS exhibits slightly different saturation voltage test conditions (2.8 V @ 40 mA, 2 A versus 2.5 V @ 30 mA, 1.5 A) and DC current gain measurement point (2 A versus 1.5 A). These variations remain within the Darlington transistor performance envelope.

Q: Are STMicroelectronics BD679 and BD679A parts pin-compatible with the onsemi BD679G?

A: The BD679 and BD679A from STMicroelectronics are supplied in SOT-32-3 package configuration, while the BD679G is supplied in TO-126 package. Although both are Through Hole packages with three leads, the physical footprints differ. PCB layout modification is required for package substitution. Electrical pin assignment (base, collector, emitter) remains consistent across all parts.

Q: What is the significance of the "A" suffix in BD679A and BD679AS?

A: The "A" suffix indicates a variant with modified electrical specifications. BD679A and BD679AS exhibit saturation voltage of 2.8 V @ 40 mA, 2 A and DC current gain specified at 2 A collector current, compared to the base BD679G specification of 2.5 V @ 30 mA, 1.5 A and gain at 1.5 A. These variants maintain the same maximum ratings and are suitable for applications where the modified test conditions align with circuit operating points.

Q: Can I use BD679 or BD679A from STMicroelectronics if my PCB is designed for TO-126 package?

A: No. The BD679 and BD679A are supplied in SOT-32-3 package, which has a different physical footprint than the TO-126 package. PCB redesign is required to accommodate the alternative package. If TO-126 package compatibility is mandatory, use BD679AS (onsemi) or BD681G (onsemi).

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed—BD681G, BD679AS, BD679 (STMicroelectronics), and BD679A (STMicroelectronics)—are ROHS3 compliant and REACH unaffected, maintaining regulatory compliance equivalent to the original BD679G.

Q: What is the maximum operating temperature for each substitute part?

A: The BD679G, BD681G, and BD679 (STMicroelectronics) are rated to 150°C junction temperature with a specified lower temperature limit of -55°C. The BD679AS and BD679A specify 150°C maximum junction temperature without explicit lower temperature specification in the provided data. All parts operate within the -55°C to 150°C range for the BD679G and BD681G.