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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics BD237

Name: BD237
Brand: STMicroelectronics
SKU: BD237
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD237

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD237.pdf

Description:: TRANS NPN 80V 2A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:4,658

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Product details

Overview

BD237 from STMicroelectronics is a low-voltage NPN power transistor in SOT-32 (TO-126) package, designed for linear and switching power amplification with V_CEO = 80 V, I_C = 2 A, and V_CE(sat) = 0.6 V at I_C = 1 A / I_B = 0.1 A. It delivers high DC current gain (h_FE ≥ 25 at I_C = 1 A) and operates up to 150 °C junction temperature, commonly used in audio output stages and DC-DC converter switches.

For engineers reviewing the BD237 datasheet, BD237 pinout, BD237 application, or BD237 equivalent, key selection criteria include saturation voltage under 1 A drive, safe operating area at T_case = 25 °C, thermal derating above 25 °C, and compatibility with TO-126 heatsink mounting in Class AB amplifier designs.

Technical Context

The BD237 employs Planar technology with "Base Island" layout to achieve low V_CE(sat) and high h_FE simultaneously. Its V_CER = 100 V (with R_BE = 1 kΩ) enables robust operation in inductive switching circuits where base-clamping improves turn-off reliability.

Electrical behavior is characterized at T_case = 25 °C, with pulsed test conditions for V_CEO(sus) (300 µs, 1.5% duty cycle). The device exhibits h_FE = 40 min at I_C = 150 mA and drops to 25 min at I_C = 1 A, indicating gain compression under high-current conduction.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum collector-emitter voltage with open base; defines safe DC blocking capability in amplifier output or switch configurations.
I_C	2 A - Continuous collector current rating; sets maximum steady-state power handling before thermal shutdown or degradation.
V_CE(sat)	0.6 V @ I_C = 1 A, I_B = 0.1 A - Low saturation voltage minimizes conduction loss and heat generation in linear regulators and switching transistors.
h_FE	25 min @ I_C = 1 A, V_CE = 2 V - Confirmed DC current gain ensures reliable base drive sizing for 1 A load switching without overdesign.
P_TOT	25 W @ T_case = 25 °C - Total power dissipation limit at case temperature; requires heatsinking for sustained >5 W operation.
T_J(max)	150 °C - Maximum junction temperature; determines allowable thermal resistance from junction-to-case and case-to-ambient.

Pinout & Package

SOT-32 (TO-126) package: three-terminal through-hole plastic power package with integrated heatsink tab (collector-connected), suitable for PCB mounting with mechanical screw or clip heatsinking.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Low-impedance path for emitter current return; connected to ground or negative rail in common-emitter configurations.
2 (Base)	Control input	Receives forward-biased current to enable conduction; requires series resistor to limit I_B per h_FE and V_BE(on) ≈ 1.3 V.
3 (Collector)	Current source terminal	Internally bonded to metal tab; must be electrically isolated from heatsink unless circuit design permits collector-common mounting.

Key Features

Feature	Design Value
Low V_CE(sat)	0.6 V at rated 1 A ensures <1 W conduction loss, reducing heatsink size in Class AB audio outputs.
High h_FE at 1 A	Minimum 25 gain supports simple fixed-base biasing without active current mirrors in discrete power stages.
V_CER = 100 V	Enhanced collector-emitter breakdown with base resistor allows safe operation in inductive flyback scenarios.
TO-126 mechanical form	Standardized footprint and heatsink interface compatible with legacy amplifier PCB layouts and tooling.

Applications

Audio Power Amplifier

DC-DC Converter Switch

Use Scenario: Output stage of 10–20 W Class AB audio amplifier driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: NPN power switch delivering peak current >1.5 A with minimal crossover distortion.

Use Value: V_CE(sat) ≤ 0.6 V reduces idle heating and improves thermal stability versus higher-saturation alternatives.

Use Scenario: Main switching transistor in non-isolated buck converter supplying 5–12 V at up to 1.5 A.

IC Role / Device Role / Timing Role: High-current, medium-voltage unidirectional switch controlled by PWM signal.

Use Value: V_CER = 100 V accommodates inductive voltage spikes during turn-off without snubber circuitry.

Linear Voltage Regulator

Motor Driver Stage

Use Scenario: Pass transistor in adjustable 3–15 V, 1.5 A linear regulator with external error amplifier.

IC Role / Device Role / Timing Role: Series pass element dissipating variable power based on input-output differential.

Use Value: P_TOT = 25 W at T_case = 25 °C enables stable regulation across 5–10 V dropout with moderate heatsinking.

Use Scenario: H-bridge low-side driver for 12 V brushed DC motor (≤200 W).

IC Role / Device Role / Timing Role: Ground-referenced current sink controlling motor direction and speed via PWM.

Use Value: h_FE ≥ 25 at 1 A simplifies gate/base drive design using microcontroller GPIO with minimal buffer stage.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD235	V_CEO = 60 V, V_CE(sat) = 0.6 V, h_FE = 40 min @ 150 mA	Lower voltage rating limits use in >60 V supply rails or inductive loads with high L·di/dt	Select when V_CC ≤ 45 V and gain stability at low current is prioritized over high-current linearity.
MJE13005	V_CEO = 400 V, I_C = 4 A, V_CE(sat) = 1.2 V @ 2 A	Higher voltage but double saturation loss; slower switching due to larger junction capacitance	Choose only for high-voltage flyback or SMPS primary switch where BD237's 80 V rating is insufficient.

Compared with BD235, the BD237 offers +20 V V_CEO margin and better high-current gain consistency; versus MJE13005, it trades off voltage headroom for lower conduction loss and faster switching in sub-100 V applications.

Availability

BD237 is available at Aetrix Electronics and suitable for audio amplifiers, linear regulators, DC-DC converters, and brushed motor drivers requiring stable component supply and long-term industrial availability.

Supply support for BD237 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, digital, and mixed-signal ICs and discrete components for industrial, automotive, and consumer markets.

The BD237 belongs to ST's legacy bipolar power transistor family optimized for cost-sensitive, thermally constrained linear and switching power applications where TO-126 mechanical reliability and predictable gain are critical.

FAQ

What is the maximum continuous collector current for BD237 at 70°C case temperature?

At T_case = 70 °C, the BD237's maximum continuous collector current is derated to approximately 1.3 A. This follows the linear derating curve in Figure 3 of the datasheet: 25 W total dissipation at 25 °C decreases by 0.2 W/°C above 25 °C, resulting in ~20 W at 70 °C, supporting ~1.3 A with V_CE(sat) ≈ 0.6 V.

Is BD237 pin-compatible with BD238?

No, BD237 (NPN) and BD238 (PNP) are complementary devices but not pin-compatible. BD238 uses the same SOT-32 package but has reversed terminal assignments: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. Swapping them without board revision will cause circuit failure.

Can BD237 be used in avalanche mode?

No, the BD237 is not rated or characterized for repetitive avalanche operation. Its V_CEO(sus) = 80 V is specified under pulsed conditions (300 µs, 1.5% duty cycle), and no energy rating (E_AS) or ruggedness data is provided in the datasheet. Use clamping diodes or snubbers for inductive load protection.

Does BD237 meet RoHS and REACH requirements?

Yes, BD237 is manufactured in ECOPACK®-compliant versions per STMicroelectronics' environmental program. The device carries RoHS-compliant marking and meets EU REACH SVHC thresholds; full compliance documentation is available via ST's official product page under ECOPACK® grade definitions.

BD237 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 80 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 100mA, 1A

Current - Collector Cutoff (Max):: 100µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 1A, 2V

Power - Max:: 25 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32-3

BD237 FAQ

1.How can I place an order for BD237 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD237 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BD237 reliable?

The price and inventory of BD237 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD237 is usually 5 days.

3.What payment methods are accepted for BD237?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD237 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD237?

BD237 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD237 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BD237?

For technical support, including BD237 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD237 requirements.

6.How does Aetrix verify that BD237 is sourced from the original manufacturer or authorized distributors?

All BD237 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BD237 meets industry standards.

7.What is the process for return or replacement of BD237?

All BD237 units undergo pre-shipment inspection (PSI). If there is an issue with BD237, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BD237 part is unused and in its original packaging.

Return procedure for BD237:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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