MJE803 Equivalent & Substitute Parts

Part Overview

The MJE803 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, making equivalent substitute parts necessary for new designs and ongoing production requirements. The MJE803 delivers 40 W maximum power dissipation with a minimum DC current gain of 750 at specified operating conditions.

Substiute Parts

MJE803

onsemiIn Stock: 940MJE803 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 MJE803 is determined by electrical parameter equivalence across the following critical specifications:

Electrical Matching Criteria:

• Transistor topology: NPN - Darlington configuration
• Maximum collector current: 4 A
• Maximum collector-emitter breakdown voltage: 80 V
• Maximum power dissipation: 40 W
• Minimum DC current gain: 750 at specified bias conditions
• Operating temperature range: minimum upper limit of 150°C

Mechanical Compatibility:

• Through-hole mounting requirement
• Package compatibility with TO-126-3 or equivalent footprint designation

The substitute parts BD679AS, BD679, and BD679A meet these electrical and mechanical requirements. All three devices maintain the 4 A collector current rating, 80 V breakdown voltage, 40 W power rating, and 750 minimum DC current gain. Variations in saturation voltage and cutoff current remain within acceptable substitution parameters for Darlington transistor applications.

Parameter Comparison

Engineering Selection Recommendations

BD679AS (onsemi) is the primary substitute for MJE803 applications. This device maintains identical electrical specifications including Vce saturation voltage and DC current gain matching conditions. BD679AS carries active product status with ROHS3 compliance, ensuring long-term availability and regulatory alignment. The onsemi manufacturer origin provides design continuity from the original MJE803 platform.

BD679 (STMicroelectronics) serves as a secondary substitute with active product status and ROHS3 compliance. This device exhibits lower Vce saturation voltage (2.5V @ 30mA, 1.5A) compared to MJE803 specifications, resulting in reduced power dissipation during saturation operation. The STMicroelectronics BD679 offers the highest inventory availability among substitute options.

BD679A (STMicroelectronics) provides an alternative substitute with active product status and ROHS3 compliance. This device matches MJE803 Vce saturation and DC current gain specifications exactly, offering electrical equivalence with modern manufacturing standards.

All three substitute parts support through-hole mounting and maintain the 4 A collector current, 80 V breakdown voltage, and 40 W power rating required for MJE803 replacement applications. Selection between BD679AS, BD679, and BD679A depends on manufacturer preference, supply chain considerations, and specific saturation voltage requirements within the application circuit.

Frequently Asked Questions (FAQ)

Q: Can BD679AS directly replace MJE803 in existing circuit designs?

A: Yes. BD679AS maintains identical electrical specifications for collector current (4 A), collector-emitter breakdown voltage (80 V), power dissipation (40 W), and DC current gain (750 minimum). Both devices use through-hole TO-126-3 packaging and support the same mounting configuration.

Q: What is the primary difference between BD679 and BD679A?

A: Both devices are STMicroelectronics products with identical collector current, breakdown voltage, and power ratings. BD679A matches MJE803 Vce saturation specifications exactly (2.8V @ 40mA, 2A), while BD679 exhibits lower saturation voltage (2.5V @ 30mA, 1.5A). This difference affects power dissipation during transistor saturation but does not prevent substitution.

Q: Are all substitute parts RoHS compliant?

A: Yes. BD679AS, BD679, and BD679A all carry ROHS3 compliance certification. The original MJE803 is RoHS non-compliant, making these substitutes necessary for applications requiring regulatory compliance.

Q: Do package differences between TO-126 and SOT-32-3 affect substitution?

A: Both BD679 and BD679A use SOT-32-3 package designation while maintaining TO-225AA and TO-126-3 case compatibility. Through-hole mounting characteristics remain equivalent for PCB assembly purposes.

Q: What inventory considerations apply to these substitutes?

A: BD679 (STMicroelectronics) offers the highest inventory availability at 23,300 pieces. BD679AS (onsemi) provides 1,956 pieces, and BD679A (STMicroelectronics) provides 1,475 pieces. MJE803 inventory stands at 865 pieces with obsolete status.

Q: Can these substitutes operate across the full MJE803 temperature range?

A: The substitute parts specify 150°C maximum junction temperature, matching the upper limit of MJE803 (-55°C ~ 150°C). Applications requiring the full -55°C lower temperature specification should verify substitute performance at minimum operating temperature through device datasheets.