MJE802STU Equivalent & Substitute Parts

Part Overview

The MJE802STU 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-126-3 through-hole package. This device is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The MJE802STU serves applications requiring moderate-power NPN Darlington switching and amplification in through-hole form factors.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Maximum Collector Current (Ic)	4	A
Maximum Collector-Emitter Breakdown Voltage	80	V
Maximum Power Dissipation	40	W
Maximum Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—

Substitute Part Grouping Explanation

Substitute parts for the MJE802STU are qualified based on matching the following critical electrical and mechanical parameters:

Transistor Type: NPN - Darlington configuration
Maximum Collector Current: 4 A
Collector-Emitter Breakdown Voltage: 80 V
Maximum Power Dissipation: 40 W
Operating Temperature Range: 150°C (TJ)
Mounting Type: Through Hole
Package Compatibility: TO-225AA or TO-126-3 equivalent packages

The BD679 and BD679A from STMicroelectronics meet these electrical specifications. Both devices are manufactured by an established semiconductor supplier and carry active product status, ensuring long-term availability and supply chain stability. The primary difference between substitute options relates to package form factor (SOT-32-3 vs. TO-126-3) and minor variations in saturation voltage characteristics at specific operating points.

Parameter Comparison

Parameter	MJE802STU (onsemi)	BD679 (STMicroelectronics)	BD679A (STMicroelectronics)
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington
Maximum Collector Current (Ic)	4 A	4 A	4 A
Collector-Emitter Breakdown Voltage (Max)	80 V	80 V	80 V
Vce Saturation (Max)	2.5 V @ 30 mA, 1.5 A	2.5 V @ 30 mA, 1.5 A	2.8 V @ 40 mA, 2 A
DC Current Gain (hFE) (Min)	750 @ 1.5 A, 3 V	750 @ 1.5 A, 3 V	750 @ 2 A, 3 V
Maximum Power Dissipation	40 W	40 W	40 W
Operating Temperature (TJ)	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Supplier Device Package	TO-126-3	SOT-32-3	SOT-32-3
Product Status	Obsolete	Active	Active

Engineering Selection Recommendations

BD679 (STMicroelectronics) is the primary substitute for the MJE802STU. This device maintains identical electrical specifications across all critical parameters, including collector current rating, breakdown voltage, power dissipation, and DC current gain. The BD679 carries active product status with ROHS3 compliance and REACH unaffected designation, ensuring regulatory alignment and supply continuity. The SOT-32-3 package provides mechanical compatibility with TO-126-3 through-hole mounting requirements.

BD679A (STMicroelectronics) serves as an alternative substitute with identical electrical ratings. The BD679A exhibits slightly elevated saturation voltage (2.8 V vs. 2.5 V) at higher collector current conditions (2 A vs. 1.5 A), which may affect switching speed and power dissipation in specific circuit topologies. This variant is suitable for applications where the saturation voltage difference does not impact circuit performance. The BD679A also maintains active product status and full regulatory compliance.

Both substitute parts are available in production quantities with established supply chains through STMicroelectronics distribution networks.

Frequently Asked Questions (FAQ)

Q: Can the BD679 directly replace the MJE802STU in existing PCB designs?

A: The BD679 and BD679A are electrically equivalent to the MJE802STU across all specified parameters. Both devices use through-hole mounting compatible with TO-126-3 footprints. PCB layout modifications are not required for electrical substitution. Verify that the SOT-32-3 package dimensions accommodate existing board hole spacing and component clearances.

Q: What is the difference between BD679 and BD679A?

A: Both devices meet the 4 A, 80 V Darlington specifications. The BD679A exhibits higher saturation voltage (2.8 V at 2 A) compared to the BD679 (2.5 V at 1.5 A). This difference affects power dissipation during saturation. Select BD679A only if circuit design tolerates the higher saturation voltage. For general-purpose applications, BD679 is the preferred choice.

Q: Are there package form factor differences between the MJE802STU and substitute parts?

A: The MJE802STU uses TO-126-3 packaging, while both BD679 and BD679A use SOT-32-3 packaging. Both are through-hole packages with compatible pin configurations. Verify mechanical fit within the application enclosure and PCB layout before final selection.

Q: What compliance certifications apply to the substitute parts?

A: Both BD679 and BD679A carry ROHS3 compliance and REACH unaffected status. These certifications match the regulatory requirements of the obsolete MJE802STU, ensuring compatibility with current environmental and safety standards.

Q: Is the MJE802STU still available for purchase?

A: The MJE802STU is classified as obsolete. Existing inventory may be available through authorized distributors, but long-term supply is not guaranteed. BD679 and BD679A are active products with established supply chains and are recommended for new designs and production continuity.

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