BD679ASTU Equivalent & Substitute Parts

Part Overview

The BD679ASTU 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, necessitating identification of active equivalent parts for ongoing design support and procurement continuity. Substitute parts must maintain electrical performance within the specified parameter ranges while accommodating available packaging and manufacturer options.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Current - Collector (Ic) (Max)	4	A
Voltage - Collector Emitter Breakdown (Max)	80	V
Power - Max	40	W
DC Current Gain (hFE) (Min)	750	—
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BD679ASTU is determined by equivalence across the following critical parameters: transistor type (NPN - Darlington), maximum collector current (4 A), maximum collector-emitter breakdown voltage (80 V), maximum power dissipation (40 W), minimum DC current gain (750), and operating temperature rating (150°C). All substitute parts must maintain these electrical specifications. Packaging variants (TO-126-3 and SOT-32-3) are both acceptable through-hole options for this application category. Compliance certifications (RoHS3, REACH Unaffected) are maintained across all substitutes. Product status transitions from obsolete to active availability improve long-term supply chain reliability.

Parameter Comparison

Parameter	BD679ASTU (onsemi)	BD679AS (onsemi)	BD679 (STMicroelectronics)	BD679A (STMicroelectronics)
Manufacturer	onsemi	onsemi	STMicroelectronics	STMicroelectronics
Product Status	Obsolete	Active	Active	Active
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	80 V	80 V	80 V	80 V
Vce Saturation (Max) @ Ib, Ic	2.8V @ 40mA, 2A	2.8V @ 40mA, 2A	2.5V @ 30mA, 1.5A	2.8V @ 40mA, 2A
Current - Collector Cutoff (Max)	500µA	500µA	500µA	500µA
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 2A, 3V	750 @ 2A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V
Power - Max	40 W	40 W	40 W	40 W
Operating Temperature (TJ)	150°C	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Supplier Device Package	TO-126-3	TO-126-3	SOT-32-3	SOT-32-3
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

BD679AS (onsemi) provides direct substitution with identical electrical specifications and TO-126-3 packaging. This part maintains active product status and onsemi manufacturer continuity, offering the closest functional replacement for the obsolete BD679ASTU.

BD679 (STMicroelectronics) and BD679A (STMicroelectronics) are active alternatives from STMicroelectronics with equivalent electrical performance. Both parts utilize SOT-32-3 packaging, which is a through-hole variant compatible with TO-126-3 footprints. The BD679 exhibits slightly lower saturation voltage (2.5V @ 30mA, 1.5A) compared to the main part specification, while BD679A matches the saturation characteristics exactly (2.8V @ 40mA, 2A).

All substitute parts maintain ROHS3 compliance and REACH Unaffected status, ensuring regulatory alignment with the original device. Selection between onsemi and STMicroelectronics sources depends on supply chain availability, procurement agreements, and existing design qualification history.

Frequently Asked Questions (FAQ)

Q: Can BD679AS directly replace BD679ASTU in existing designs?

A: Yes. BD679AS maintains identical electrical specifications, operating temperature range, power rating, and TO-126-3 packaging. The primary difference is product status transition from obsolete to active.

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

A: Both are through-hole package variants for the BD679 series. TO-126-3 is the original package for BD679ASTU and BD679AS. SOT-32-3 is used by STMicroelectronics for BD679 and BD679A. Pin configurations and footprints are compatible for through-hole mounting applications.

Q: Are there electrical differences between BD679 and BD679A from STMicroelectronics?

A: Both parts meet the 4 A, 80 V, 40 W specifications. BD679A matches the saturation voltage specification of BD679ASTU exactly (2.8V @ 40mA, 2A), while BD679 specifies 2.5V @ 30mA, 1.5A. For applications requiring precise saturation characteristics, BD679A is the preferred STMicroelectronics option.

Q: Why is BD679ASTU classified as obsolete?

A: Obsolete status indicates the part is no longer manufactured by onsemi. Active equivalents (BD679AS, BD679, BD679A) ensure continued availability and supply chain support.

Q: Do all substitute parts comply with RoHS3 and REACH regulations?

A: Yes. BD679AS, BD679, and BD679A are all ROHS3 Compliant and REACH Unaffected, maintaining regulatory compliance with the original BD679ASTU.

Q: Which substitute offers the best inventory availability?

A: BD679 (STMicroelectronics) shows the highest inventory level at 23,300 pieces. BD679AS (onsemi) provides 1,956 pieces, and BD679A (STMicroelectronics) provides 1,475 pieces.

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