BD237STU Equivalent & Substitute Parts

Part Overview

The BD237STU is an NPN bipolar junction transistor manufactured by onsemi, rated for 80 V collector-emitter breakdown voltage and 2 A maximum collector current. This device is packaged in TO-126-3 through-hole configuration and rated for 25 W maximum power dissipation. The BD237STU is classified as obsolete product status. Identification of equivalent and substitute parts is necessary to maintain design continuity and ensure component availability for production and repair applications.

Key Parameters

Parameter	Value
Transistor Type	NPN
Voltage - Collector Emitter Breakdown (Max)	80 V
Current - Collector (Ic) (Max)	2 A
Power - Max	25 W
Vce Saturation (Max) @ Ib, Ic	600mV @ 100mA, 1A
DC Current Gain (hFE) (Min) @ Ic, Vce	25 @ 1A, 2V
Current - Collector Cutoff (Max)	100µA (ICBO)
Frequency - Transition	3MHz
Operating Temperature	150°C (TJ)
Mounting Type	Through Hole
Package / Case	TO-225AA, TO-126-3

Substitute Part Grouping Explanation

Substitution of the BD237STU is determined by electrical and mechanical compatibility across the following critical parameters: transistor type (NPN), collector-emitter breakdown voltage (80 V), maximum collector current rating, power dissipation capability, saturation voltage characteristics, DC current gain, and through-hole mounting configuration.

Substitute parts are grouped into two categories:

Direct Electrical Equivalents: Parts maintaining identical or superior ratings across all critical electrical parameters while accommodating the same voltage and current specifications. These parts support direct replacement in applications where the BD237STU was originally specified.

Similar Electrical Alternatives: Parts with modified electrical characteristics that remain compatible within the 80 V breakdown voltage class and through-hole package family. These alternatives are suitable for applications where collector current or power dissipation requirements differ from the original specification, provided circuit design accommodates the parameter variations.

The following parameters establish substitution validity:

Collector-emitter breakdown voltage: 80 V (fixed requirement)
Transistor type: NPN (fixed requirement)
Mounting type: Through Hole (fixed requirement)
Package family: TO-126-3 or equivalent through-hole package
Maximum collector current: 2 A or greater
Maximum power dissipation: 25 W or greater
Saturation voltage: 600mV or less at specified test conditions
DC current gain: 25 or greater at specified test conditions

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max)	Vce Breakdown (Max)	Power (Max)	Vce Sat (Max)	hFE (Min)	Package	Frequency
BD237STU	onsemi	Obsolete	2 A	80 V	25 W	600mV @ 100mA, 1A	25 @ 1A, 2V	TO-126-3	3MHz
BD237G	onsemi	Active	2 A	80 V	25 W	600mV @ 100mA, 1A	25 @ 1A, 2V	TO-126	3MHz
BD237	STMicroelectronics	Active	2 A	80 V	25 W	600mV @ 100mA, 1A	25 @ 1A, 2V	SOT-32-3	—
2N5192G	onsemi	Active	4 A	80 V	40 W	1.4V @ 1A, 4A	20 @ 1.5A, 2V	TO-126	2MHz
2N4923G	onsemi	Active	1 A	80 V	30 W	600mV @ 100mA, 1A	30 @ 500mA, 1V	TO-126	3MHz
BD139G	onsemi	Active	1.5 A	80 V	12.5 W	500mV @ 50mA, 500mA	40 @ 150mA, 2V	TO-126	—
BD139	STMicroelectronics	Active	1.5 A	80 V	1.25 W	500mV @ 50mA, 500mA	40 @ 150mA, 2V	SOT-32-3	—
BD139-10	STMicroelectronics	Active	1.5 A	80 V	1.25 W	500mV @ 50mA, 500mA	40 @ 150mA, 2V	SOT-32	—
BD139-16	STMicroelectronics	Active	1.5 A	80 V	1.25 W	500mV @ 50mA, 500mA	40 @ 150mA, 2V	SOT-32-3	—
BD441G	onsemi	Active	4 A	80 V	36 W	800mV @ 300mA, 3A	40 @ 500mA, 1V	TO-126	3MHz

Engineering Selection Recommendations

Primary Recommendation: BD237G (onsemi)

The BD237G is the direct active-status equivalent to the BD237STU. This part maintains identical electrical specifications across all critical parameters: 2 A maximum collector current, 80 V breakdown voltage, 25 W power rating, and 3 MHz transition frequency. The BD237G is manufactured by onsemi, the original manufacturer of the BD237STU, and carries active product status with high inventory availability (11,547 units). Both parts comply with ROHS3 and REACH requirements. The BD237G is packaged in TO-126 configuration, which is mechanically compatible with the original TO-126-3 specification. This substitution requires no circuit redesign.

Secondary Recommendation: BD237 (STMicroelectronics)

The BD237 from STMicroelectronics provides identical electrical specifications to the BD237STU with active product status and substantial inventory (21,100 units). This part maintains 2 A collector current, 80 V breakdown voltage, and 25 W power dissipation. The primary distinction is packaging: the STMicroelectronics BD237 is supplied in SOT-32-3 configuration rather than TO-126-3. PCB layout modification is required to accommodate the different package footprint. Both parts comply with ROHS3 and REACH requirements. This substitution is suitable when package footprint modification is feasible.

Alternative Recommendations for Modified Current Requirements:

For applications where collector current requirements differ from the original 2 A specification:

2N5192G (onsemi): Rated for 4 A maximum collector current with 40 W power dissipation and 80 V breakdown voltage. Suitable for applications requiring higher current capacity. Transition frequency is 2MHz (reduced from 3MHz). Active product status with 10,300 units available.
2N4923G (onsemi): Rated for 1 A maximum collector current with 30 W power dissipation and 80 V breakdown voltage. Suitable for applications with reduced current requirements. Active product status with 5,921 units available.

Not Recommended for Direct Substitution:

BD139 series parts (BD139, BD139-10, BD139-16, BD139G) are not suitable direct substitutes for the BD237STU. These parts are rated for maximum 1.5 A collector current, which is below the 2 A specification of the BD237STU. Additionally, most BD139 variants are rated for 1.25 W power dissipation, significantly below the 25 W rating of the original part. These parts are suitable only for applications where the circuit design has been modified to accommodate reduced current and power specifications.

BD441G is not recommended as a direct substitute despite higher current rating (4 A) due to elevated saturation voltage (800mV at 3A) compared to the BD237STU specification (600mV at 1A), which may affect circuit performance in saturation-mode applications.

Frequently Asked Questions (FAQ)

Q: Can BD237G be used as a direct replacement for BD237STU without circuit modification?

A: Yes. The BD237G maintains identical electrical specifications across all critical parameters: 2 A maximum collector current, 80 V collector-emitter breakdown voltage, 25 W power dissipation, 600mV saturation voltage at specified test conditions, and 3 MHz transition frequency. The TO-126 package is mechanically compatible with TO-126-3 footprints. No circuit redesign is required.

Q: What is the difference between BD237G and BD237 from STMicroelectronics?

A: Both parts provide identical electrical specifications. The primary difference is packaging: BD237G uses TO-126 configuration while the STMicroelectronics BD237 uses SOT-32-3 configuration. These packages have different physical dimensions and PCB footprints. Selection depends on available PCB layout space and manufacturing capability to accommodate the specific package type.

Q: Why are BD139 series parts not recommended as substitutes?

A: BD139 series parts are rated for maximum 1.5 A collector current, which is below the 2 A specification of the BD237STU. Most BD139 variants are also rated for 1.25 W power dissipation, significantly lower than the 25 W rating of the original part. These parts are suitable only for applications where circuit design has been modified to operate within reduced current and power specifications.

Q: Can 2N5192G be used in place of BD237STU?

A: 2N5192G is electrically compatible with the 80 V breakdown voltage class and provides higher current capacity (4 A) and power dissipation (40 W). However, this part exhibits higher saturation voltage (1.4V at 4A) compared to the BD237STU (600mV at 1A) and lower transition frequency (2MHz versus 3MHz). Use of 2N5192G is suitable only for applications where circuit design accommodates these parameter differences, particularly in saturation-mode switching applications where the higher saturation voltage may affect performance.

Q: What is the significance of product status (Active vs. Obsolete)?

A: Product status indicates manufacturer support and availability. The BD237STU is classified as obsolete, meaning onsemi no longer manufactures this part and existing inventory will eventually deplete. Active-status parts such as BD237G, BD237, and 2N5192G are currently manufactured and supported by their respective manufacturers, ensuring long-term availability for production and repair applications. Selection of active-status substitutes is recommended for new designs and ongoing production.

Q: Are all substitute parts ROHS3 and REACH compliant?

A: Yes. All substitute parts listed in this reference maintain ROHS3 compliance and REACH unaffected status, consistent with the original BD237STU. This ensures compatibility with environmental and regulatory requirements across all listed alternatives.

Q: What package options are available for BD237 equivalents?

A: The BD237STU is originally packaged in TO-126-3 through-hole configuration. Equivalent parts are available in the following packages: TO-126 (BD237G), SOT-32-3 (BD237 from STMicroelectronics), and SOT-32 (BD139-10). Package selection depends on PCB layout requirements and manufacturing equipment capability. All packages are through-hole configurations suitable for manual or automated assembly.

Q: Can multiple substitute parts be used interchangeably in the same application?

A: No. Each substitute part has distinct electrical characteristics that determine suitability for specific applications. BD237G and BD237 (STMicroelectronics) are direct electrical equivalents suitable for applications originally designed for BD237STU. Parts with modified current ratings (2N5192G at 4A, 2N4923G at 1A) are suitable only for applications where circuit design accommodates the different specifications. Verification of electrical compatibility with the specific application circuit is required before substitution.

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