BD679 NPN Darlington Transistor Equivalent & Substitute Parts

Part Overview

The BD679 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 component is classified as obsolete, necessitating identification of active equivalent alternatives for new designs and ongoing production requirements. Substitute parts maintain electrical performance specifications while offering improved product status and regulatory compliance.

Substiute Parts

BD679

onsemiIn Stock: 23328BD679 Datasheet

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BD679AS

onsemiIn Stock: 1998BD679AS Datasheet

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BD679

STMicroelectronicsIn Stock: 23392BD679 Datasheet

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BD679A

STMicroelectronicsIn Stock: 1566BD679A Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD679 is determined by equivalence in the following electrical and mechanical parameters: maximum collector current (4 A), collector-emitter breakdown voltage (80 V), maximum power dissipation (40 W), minimum DC current gain (750), collector cutoff current (500 µA), and Through Hole mounting configuration. All substitute parts maintain these core specifications, ensuring functional compatibility in existing circuit designs.

Substitute parts are grouped into two categories based on package configuration: TO-126-3 package variants and SOT-32-3 package variants. Package selection depends on printed circuit board layout and mechanical mounting requirements. All substitute parts are manufactured by either onsemi or STMicroelectronics and carry active product status with RoHS3 compliance.

Parameter Comparison

Engineering Selection Recommendations

BD679AS (onsemi) is the direct successor to the obsolete BD679 from the same manufacturer. This part maintains identical electrical specifications and is supplied in TO-126-3 package configuration. BD679AS carries active product status and RoHS3 compliance, making it suitable for new designs and production environments with regulatory requirements.

BD679 (STMicroelectronics) provides electrical equivalence with identical saturation voltage and current gain specifications at the original test conditions. This part is supplied in SOT-32-3 package and carries active product status with RoHS3 compliance. Selection of this variant is appropriate when STMicroelectronics supply chain or packaging preferences are required.

BD679A (STMicroelectronics) offers electrical equivalence with modified saturation voltage and current gain test conditions (2.8V @ 40mA, 2A and 750 @ 2A, 3V respectively). This part is supplied in SOT-32-3 package and carries active product status with RoHS3 compliance. This variant is suitable for applications where the modified test conditions align with circuit operating points.

All substitute parts maintain the 4 A collector current, 80 V breakdown voltage, 40 W power rating, and 500 µA collector cutoff current specifications of the original BD679. Selection between TO-126-3 and SOT-32-3 package variants depends on printed circuit board layout and mechanical mounting requirements.

Frequently Asked Questions (FAQ)

Q: Can BD679AS be used as a direct replacement for the obsolete BD679?

A: Yes. BD679AS maintains identical electrical specifications including 4 A maximum collector current, 80 V breakdown voltage, 40 W power rating, and 750 minimum DC current gain. Both parts are manufactured by onsemi and use compatible Through Hole mounting. The primary difference is product status (active versus obsolete) and RoHS3 compliance of BD679AS.

Q: What is the difference between TO-126-3 and SOT-32-3 package options?

A: Both packages are Through Hole configurations suitable for the same electrical specifications. Package selection depends on printed circuit board layout and mechanical mounting requirements. TO-126-3 is the standard package for onsemi BD679AS. SOT-32-3 is the package configuration for STMicroelectronics BD679 and BD679A variants. Verify printed circuit board footprint compatibility before selection.

Q: Are there differences in saturation voltage between substitute parts?

A: Yes. The original BD679 and STMicroelectronics BD679 specify 2.5V saturation voltage at 30mA base current and 1.5A collector current. BD679AS and STMicroelectronics BD679A specify 2.8V saturation voltage at 40mA base current and 2A collector current. These differences reflect different test conditions and do not affect functional compatibility in most applications. Verify saturation voltage requirements for your specific circuit design.

Q: Which substitute part should be selected for new designs?

A: BD679AS (onsemi) is recommended for new designs as the direct active successor from the original manufacturer. This part carries RoHS3 compliance and maintains the original electrical specifications and TO-126-3 package configuration. STMicroelectronics variants (BD679 and BD679A) are suitable alternatives when STMicroelectronics supply chain or SOT-32-3 package configuration is preferred.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. BD679AS, BD679 (STMicroelectronics), and BD679A (STMicroelectronics) all carry RoHS3 compliance. The original obsolete BD679 from onsemi is RoHS non-compliant. Compliance status is relevant for applications subject to RoHS regulations.

Q: What is the operating temperature range for substitute parts?

A: BD679AS, BD679 (STMicroelectronics), and BD679A (STMicroelectronics) all specify maximum junction temperature of 150°C. The original BD679 specifies -55°C to 150°C operating range. Verify that the 150°C maximum junction temperature specification meets your application requirements.