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

STMicroelectronics BD441

Name: BD441
Brand: STMicroelectronics
SKU: BD441
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD441

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BD441.pdf

Description:: TRANS NPN 80V 4A SOT-32

Quantity:: RFQ Add To RFQ list

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Inventory:2,846

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Product details

Overview

BD441 from STMicroelectronics is an NPN silicon power transistor in SOT-32 (TO-126) package, rated for 80 V V_CEO, 4 A I_C, and 36 W P_TOT at T_case = 25 °C. It delivers high DC current gain (h_FE up to 140 at I_C = 2 A) and low saturation voltage (V_CE(sat) = 0.8 V @ I_C = 2 A, I_B = 0.2 A), enabling efficient linear regulation and hard-switching in industrial motor drives and power supplies.

For engineers reviewing the BD441 datasheet, BD441 pinout, BD441 application, or BD441 equivalent, key selection criteria include verified V_CEO/I_C derating curves, h_FE stability across I_C = 10 mA–2 A, V_CE(sat) under pulsed load conditions, thermal resistance R_thJC = 0.97 °C/W, and compatibility with non-inductive resistive switching test circuits per Figure 9.

Technical Context

The BD441 employs planar "base island" layout to achieve high β uniformity and low V_CE(sat) simultaneously. Its rugged 150 °C maximum junction temperature and 80 V collector-base breakdown support operation in unregulated DC rails and inductive load snubbing.

Electrical behavior is characterized at T_case = 25 °C with defined pulse conditions: V_CEO(sus) tested at 300 ms pulse width and ≥1.5% duty cycle; switching times measured using fast electronic switch and non-inductive resistor per Figure 9.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum safe collector-emitter voltage with base open; defines rail tolerance in linear regulators and flyback clamp circuits.
I_C	4 A continuous - Rated collector current at T_case = 25 °C; requires heatsinking above ~1.5 A in sustained operation.
P_TOT	36 W - Total power dissipation limit at 25 °C case temperature; derates linearly to zero at 150 °C junction.
h_FE	15–140 - DC current gain range across I_C = 10 mA to 2 A; enables stable bias design in Class AB amplifiers and relay drivers.
V_CE(sat)	0.8 V @ I_C = 2 A, I_B = 0.2 A - Low saturation voltage minimizes conduction loss in switching applications.
R_thJC	0.97 °C/W - Junction-to-case thermal resistance; determines heatsink size needed for target T_J under given P_D.

Pinout & Package

SOT-32 (TO-126) package: molded plastic case with copper leadframe, 3-pin through-hole mounting, ECOPACK® lead-free second-level interconnect, JEDEC-compliant marking and labeling.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Low-impedance return path; connected to ground or negative rail in common-emitter configurations.
2 (Collector)	Current source terminal	High-current output node; directly interfaces with inductive loads or power rails up to 80 V.
3 (Base)	Control input terminal	Current-driven gate; requires 0.2 A drive for full saturation at 2 A collector load.

Key Features

Feature	Design Value
Planar "base island" structure	Enables simultaneous high h_FE and low V_CE(sat) without trade-off between gain and conduction loss.
ECOPACK® packaging	Lead-free second-level interconnect compliant with JEDEC JESD97; supports RoHS-constrained industrial assembly.
150 °C max junction temperature	Permits operation in enclosed enclosures or high-ambient environments without forced air cooling.
V_CEO(sus) = 80 V (pulsed)	Validated sustaining voltage under 300 ms pulses; ensures reliability during transient overvoltage events.

Applications

Industrial Linear Regulators

DC Motor Control Drivers

Use Scenario: Unregulated 24–72 V DC input converted to stable 5–15 V output for PLC I/O modules.

IC Role / Device Role / Timing Role: Pass transistor in series-regulator topology, dissipating excess voltage as heat.

Use Value: Low V_CE(sat) reduces dropout voltage and thermal load; high h_FE eases base drive design with low-power op-amp error amplifiers.

Use Scenario: H-bridge half-bridge leg driving 12–48 V brushed DC motors in factory automation actuators.

IC Role / Device Role / Timing Role: Switching element controlling motor direction and speed via PWM at ≤20 kHz.

Use Value: 4 A I_C rating supports peak stall currents; rugged V_CEO withstands back-EMF spikes up to 80 V.

Switch-Mode Power Supply Output Stage

Relay and Solenoid Interface Circuits

Use Scenario: Secondary-side synchronous rectifier or linear post-regulator in 100–500 W AC/DC adapters.

IC Role / Device Role / Timing Role: High-current switching device in discontinuous conduction mode (DCM) flyback or forward converter output stage.

Use Value: Verified 7 A I_CM peak rating handles short-duration overload transients; low R_thJC enables compact heatsink integration.

Use Scenario: Driving 24 V/1 A industrial relays and 12 V/2 A solenoids in HVAC control panels.

IC Role / Device Role / Timing Role: Single-ended switch interfacing microcontroller GPIO to inductive load.

Use Value: 80 V V_CEO safely clamps flyback voltage from relay coils; 1 A I_B rating allows direct drive from logic-level buffers.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD439	Same SOT-32 package; lower h_FE (min 20 vs. 15) and identical V_CEO/I_C ratings.	Less suitable for low-base-drive designs; acceptable where gain margin is relaxed.	Select BD439 only if h_FE > 40 not required and cost sensitivity outweighs gain headroom.
MJE13009	TO-220 package; higher I_C (12 A) but lower V_CEO (400 V) and no V_CEO(sus) spec.	Requires larger PCB footprint and different heatsink interface; used in SMPS primary side.	Choose MJE13009 only when higher voltage blocking or higher current is mandatory and TO-220 mounting is acceptable.

Compared with BD439 and MJE13009, the BD441 uniquely balances high h_FE, low V_CE(sat), and 80 V V_CEO in the compact SOT-32 form factor-making it optimal for space-constrained industrial linear and switching stages where base drive efficiency and thermal density matter.

Availability

BD441 is available at Aetrix Electronics and suitable for industrial motor control, linear power regulation, relay/solenoid interface, and switch-mode power supply output stages requiring stable component supply and long-term manufacturability.

Supply support for BD441 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, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The BD441 belongs to ST's legacy bipolar power transistor family, engineered specifically for robust linear and switching operation in industrial equipment where reliability under thermal stress and consistent gain performance are critical.

FAQ

What is the maximum safe operating temperature for BD441?

The BD441 has a maximum junction temperature (T_J) of 150 °C and a storage temperature range of –65 to +150 °C. Safe operation requires maintaining T_J ≤ 150 °C via appropriate heatsinking-calculated using R_thJC = 0.97 °C/W and ambient conditions. Exceeding this limit risks permanent parametric shift or thermal runaway.

Can BD441 replace BD442 in a circuit?

No-BD441 is NPN while BD442 is its complementary PNP counterpart. They share identical voltage/current ratings and package but opposite polarity. Swapping them would reverse current flow and disable biasing; use BD442 only in PNP positions such as emitter-follower stages or complementary push-pull outputs.

Is BD441 suitable for automotive applications?

ST does not specify BD441 as automotive-grade. Its datasheet explicitly states that non-automotive-grade ST products are used in automotive applications at the user's own risk. For automotive use, qualified alternatives like the STL12DN4LF5 (N-channel MOSFET) or AUIRFZ44N should be evaluated per AEC-Q101 requirements.

What is the typical switching time for BD441 in resistive load circuits?

Per Figure 7 and Figure 8 in the official datasheet, BD441 exhibits t_on ≈ 0.8 µs and t_off ≈ 1.2 µs into a 100 Ω resistive load at I_C = 2 A. These values assume fast electronic switching and non-inductive load conditions per Figure 9 test circuit-actual times increase with inductive loads or insufficient base drive.

BD441 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 4 A

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

Vce Saturation (Max) @ Ib, Ic:: 800mV @ 200mA, 2A

Current - Collector Cutoff (Max):: 100µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 500mA, 1V

Power - Max:: 36 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32

BD441 FAQ

1.How can I place an order for BD441 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD441 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 BD441 reliable?

The price and inventory of BD441 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD441 is usually 5 days.

3.What payment methods are accepted for BD441?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD441 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD441?

BD441 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD441 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 BD441?

For technical support, including BD441 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD441 requirements.

6.How does Aetrix verify that BD441 is sourced from the original manufacturer or authorized distributors?

All BD441 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 BD441 meets industry standards.

7.What is the process for return or replacement of BD441?

All BD441 units undergo pre-shipment inspection (PSI). If there is an issue with BD441, 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 BD441 part is unused and in its original packaging.

Return procedure for BD441:

1.Submit a request within 90 days.

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

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