2N6039G Equivalent & Substitute Parts

Part Overview

The 2N6039G 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 and substitute parts necessary for ongoing design support and production continuity. The 2N6039G delivers 40 W maximum power dissipation and operates across a temperature range of -65°C to 150°C (junction temperature).

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Voltage - Collector Emitter Breakdown (Max)	80	V
Current - Collector (Ic) (Max)	4	A
Power - Max	40	W
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 2A, 3V	—
Operating Temperature Range	-65 to 150	°C (TJ)
Mounting Type	Through Hole	—
Package / Case	TO-126-3	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the 2N6039G is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN - Darlington configuration
Collector-emitter breakdown voltage must equal or exceed 80 V
Maximum collector current must equal or exceed 4 A
Maximum power dissipation must equal or exceed 40 W
DC current gain (hFE) must meet or exceed 750 @ specified test conditions
Operating temperature range must accommodate the application requirements

Mechanical Compatibility Criteria:

Mounting type must be through-hole
Package footprint must be compatible with TO-126 or equivalent mechanical envelope

Compliance Criteria:

RoHS3 compliance required
REACH unaffected status required

Substitute parts are grouped into two categories: direct electrical equivalents (matching all electrical parameters within specified tolerances) and similar parts (meeting electrical requirements with voltage or current ratings that exceed the original specification).

Parameter Comparison

Parameter	2N6039G (Main)	BD679AS	BD681G	BD679A	BD679
Manufacturer	onsemi	onsemi	onsemi	STMicroelectronics	STMicroelectronics
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Voltage - Collector Emitter Breakdown (Max)	80 V	80 V	100 V	80 V	80 V
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A	4 A
Power - Max	40 W	40 W	40 W	40 W	40 W
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 2A, 3V	750 @ 2A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V	750 @ 1.5A, 3V
Operating Temperature Range	-65 to 150°C	150°C (Max)	-55 to 150°C	150°C (Max)	150°C (Max)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Supplier Device Package	TO-126	TO-126-3	TO-126	SOT-32-3	SOT-32-3
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

BD679AS (onsemi) is a direct electrical equivalent to the 2N6039G. This part maintains identical voltage and current ratings (80 V, 4 A), matching power dissipation (40 W), and equivalent DC current gain specifications. BD679AS is manufactured by onsemi, the same original manufacturer, and carries active product status with full RoHS3 compliance. The TO-126-3 package provides mechanical compatibility with the original TO-126 footprint. This substitute is suitable for direct replacement in applications requiring the full -65°C to 150°C operating range, noting that BD679AS specifies a maximum junction temperature of 150°C.

BD681G (onsemi) is a similar part with enhanced voltage rating (100 V versus 80 V). This device maintains the 4 A collector current and 40 W power rating, making it suitable for applications where higher voltage margin is beneficial. BD681G is active and RoHS3 compliant. The extended operating temperature range (-55°C to 150°C) accommodates most industrial applications. The TO-126 package matches the original mechanical envelope. BD681G is appropriate for designs where voltage derating or higher transient voltage tolerance is required.

BD679A (STMicroelectronics) provides electrical equivalence to the 2N6039G with identical voltage (80 V) and current (4 A) specifications. This part is manufactured by STMicroelectronics and carries active product status with RoHS3 compliance. The SOT-32-3 package differs mechanically from the original TO-126, requiring PCB layout modification. BD679A is suitable for new designs or redesigns where package footprint change is acceptable.

BD679 (STMicroelectronics) is a similar part offering electrical equivalence at 80 V and 4 A ratings. This device is active and RoHS3 compliant, manufactured by STMicroelectronics. The SOT-32-3 package requires mechanical redesign. BD679 is appropriate for applications where package footprint flexibility exists.

For applications requiring the lowest design risk and fastest implementation, BD679AS is the preferred substitute due to manufacturer continuity and package compatibility. For applications where voltage margin enhancement is desired, BD681G is the appropriate selection. Substitutes requiring SOT-32-3 packages (BD679A, BD679) necessitate PCB redesign and are suitable for new product development or planned redesigns.

Frequently Asked Questions (FAQ)

Q: Can BD679AS directly replace 2N6039G without PCB modification?

A: Yes. BD679AS maintains identical electrical specifications (80 V, 4 A, 40 W) and uses the TO-126-3 package, which is mechanically compatible with the original TO-126 footprint. No PCB layout changes are required.

Q: What is the primary difference between BD679AS and BD681G?

A: BD681G has a higher collector-emitter breakdown voltage rating (100 V versus 80 V). Both devices deliver 4 A maximum collector current and 40 W power dissipation. BD681G is selected when higher voltage margin or transient voltage protection is required.

Q: Why do BD679A and BD679 require PCB modification?

A: These parts use the SOT-32-3 package instead of the TO-126 package used by the 2N6039G. The SOT-32-3 package has a different mechanical footprint and pin layout, requiring PCB redesign for implementation.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts (BD679AS, BD681G, BD679A, BD679) carry RoHS3 compliance certification, matching the original 2N6039G compliance status.

Q: What is the operating temperature difference between 2N6039G and its substitutes?

A: The 2N6039G operates from -65°C to 150°C (junction temperature). BD679AS, BD679A, and BD679 specify a maximum junction temperature of 150°C without a stated minimum. BD681G operates from -55°C to 150°C. Applications requiring operation below -55°C must retain the original 2N6039G or confirm substitute suitability with the manufacturer.

Q: Can BD681G be used in place of 2N6039G in all applications?

A: BD681G is suitable for most applications due to its higher voltage rating (100 V) and equivalent current/power specifications. The extended voltage rating provides additional design margin. Confirm that the -55°C to 150°C operating range accommodates your application requirements.

Q: Which substitute offers the best long-term availability?

A: BD679AS and BD681G, both manufactured by onsemi, carry active product status. BD679 and BD679A, manufactured by STMicroelectronics, also carry active status. Active product status indicates ongoing manufacturing and supply availability compared to the obsolete 2N6039G.

Q: Are there differences in DC current gain (hFE) between substitutes?

A: All substitutes maintain the minimum DC current gain specification of 750. BD679AS and BD679A specify hFE @ 2A, 3V. BD681G and BD679 specify hFE @ 1.5A, 3V. These differences reflect test condition variations rather than functional performance differences in typical applications.

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