BD139 NPN Bipolar Junction Transistor Equivalent & Substitute Parts

Part Overview

The BD139 is an NPN bipolar junction transistor manufactured by onsemi, rated for 80 V collector-emitter breakdown voltage and 1.5 A maximum collector current. The device is packaged in TO-126 through-hole configuration and is classified as obsolete product status. Due to its obsolete classification, equivalent and substitute parts from active product lines are necessary for ongoing design support and procurement continuity. Substitute parts maintain electrical compatibility while offering improved availability and compliance certifications.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	80	V
Current - Collector (Ic) (Max)	1.5	A
Power - Max	1.25	W
Vce Saturation (Max) @ Ib, Ic	500mV @ 50mA, 500mA	—
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) (Min) @ Ic, Vce	40	@ 150mA, 2V
Operating Temperature	-55 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—

Substitute Part Grouping Explanation

Substitution of the BD139 is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Substitution Parameters:

Transistor Type: NPN
Voltage - Collector Emitter Breakdown (Max): 80 V
Current - Collector (Ic) (Max): 1.5 A
Vce Saturation (Max) @ Ib, Ic: 500mV @ 50mA, 500mA
Current - Collector Cutoff (Max): 100nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce: 40 @ 150mA, 2V
Operating Temperature: -55°C to 150°C (TJ)
Mounting Type: Through Hole
Package / Case: TO-225AA, TO-126-3

Substitute parts are grouped into two categories:

Direct Equivalents: Parts maintaining identical electrical specifications and compatible packaging (TO-126 or TO-126-3 variants). These include BD139G (onsemi), BD13910S (Fairchild Semiconductor), BD13910STU (onsemi), and BD13916STU (onsemi).

Variant Equivalents: Parts with identical electrical specifications but different supplier device packaging designations (SOT-32 or SOT-32-3). These include BD139 (STMicroelectronics), BD139-10 (STMicroelectronics), and BD139-16 (STMicroelectronics).

All substitute parts satisfy the core electrical requirements and through-hole mounting configuration of the original BD139.

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	Vce Breakdown (Max)	Power (Max)	hFE (Min)	Package	Product Status	RoHS Status
BD139	onsemi	1.5 A	80 V	1.25 W	40	TO-126-3	Obsolete	Non-compliant
BD139G	onsemi	1.5 A	80 V	12.5 W	40	TO-126-3	Active	ROHS3 Compliant
BD13910S	Fairchild Semiconductor	1.5 A	80 V	1.25 W	63	TO-126-3	Active	Not specified
BD13910STU	onsemi	1.5 A	80 V	1.25 W	63	TO-126-3	Active	ROHS3 Compliant
BD13916STU	onsemi	1.5 A	80 V	1.25 W	100	TO-126-3	Active	ROHS3 Compliant
BD139	STMicroelectronics	1.5 A	80 V	1.25 W	40	SOT-32-3	Active	ROHS3 Compliant
BD139-10	STMicroelectronics	1.5 A	80 V	1.25 W	40	SOT-32	Active	ROHS3 Compliant
BD139-16	STMicroelectronics	1.5 A	80 V	1.25 W	40	SOT-32-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

For RoHS3 Compliance Requirements: BD139G (onsemi), BD13910STU (onsemi), BD13916STU (onsemi), BD139 (STMicroelectronics), BD139-10 (STMicroelectronics), and BD139-16 (STMicroelectronics) all satisfy ROHS3 compliance. The original BD139 (onsemi) is RoHS non-compliant and should be replaced in new designs requiring regulatory compliance.

For Active Product Status: All substitute parts listed maintain active product status, ensuring long-term availability and manufacturing support. The original BD139 (onsemi) is classified as obsolete.

For Identical Electrical Performance: BD139G (onsemi) and BD139 (STMicroelectronics) maintain the minimum DC current gain specification of 40 @ 150mA, 2V, matching the original part. BD13910S, BD13910STU, and BD13916STU offer higher DC current gain specifications (63 and 100 respectively), which remain within acceptable substitution parameters for NPN transistor applications.

For Package Compatibility: TO-126-3 packaged variants (BD139G, BD13910S, BD13910STU, BD13916STU) provide direct mechanical compatibility with original through-hole PCB layouts. SOT-32 and SOT-32-3 variants (BD139, BD139-10, BD139-16 from STMicroelectronics) require PCB footprint verification before selection.

For Power Dissipation: BD139G (onsemi) is rated for 12.5 W maximum power, providing enhanced thermal performance compared to the 1.25 W rating of the original BD139. This higher rating does not affect substitution compatibility and may improve thermal margin in existing designs.

Frequently Asked Questions (FAQ)

Q: Can BD139G directly replace the original BD139 in existing designs?

A: Yes. BD139G maintains identical electrical specifications (80 V breakdown, 1.5 A collector current, 500mV saturation voltage, 40 minimum hFE) and compatible TO-126-3 through-hole packaging. The higher power rating (12.5 W vs. 1.25 W) does not affect circuit operation and improves thermal performance.

Q: What is the difference between BD13910STU and BD13916STU?

A: Both parts are onsemi products in TO-126-3 packaging with identical voltage, current, and saturation specifications. The primary difference is DC current gain: BD13910STU specifies 63 minimum hFE, while BD13916STU specifies 100 minimum hFE. Both values exceed the original BD139 specification of 40 minimum hFE and remain within acceptable substitution parameters.

Q: Are STMicroelectronics BD139 variants (BD139, BD139-10, BD139-16) compatible with original PCB layouts?

A: Electrical compatibility is confirmed. However, these parts use SOT-32 or SOT-32-3 package designations rather than TO-126-3. PCB footprint verification is required before selection, as package outlines may differ despite similar through-hole mounting.

Q: Why is the original BD139 (onsemi) classified as obsolete?

A: Product status reflects manufacturer discontinuation. Substitute parts from active product lines (onsemi BD139G, Fairchild BD13910S, STMicroelectronics variants) provide equivalent functionality with improved availability and compliance certifications.

Q: Which substitute part offers the best RoHS compliance?

A: All recommended substitute parts (BD139G, BD13910STU, BD13916STU, and STMicroelectronics variants) are ROHS3 compliant. The original BD139 (onsemi) is RoHS non-compliant and should be replaced in designs requiring regulatory compliance.

Q: Can higher hFE variants (BD13910STU, BD13916STU) affect circuit performance?

A: Higher DC current gain does not degrade circuit performance in standard BJT applications. These variants maintain identical voltage and current ratings, saturation characteristics, and operating temperature range. Higher hFE may reduce base drive requirements in current-limited applications.

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

A: Both are three-lead through-hole packages for NPN transistors. TO-126-3 and SOT-32-3 designations indicate different standardization bodies and potential outline variations. Physical verification against PCB footprint is required before substituting between these package types.

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