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

onsemi BD441G

Name: BD441G
Brand: onsemi
SKU: BD441G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD441G

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BD441G.pdf

Description:: TRANS NPN 80V 4A TO-126

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD441G from ON Semiconductor is a medium-power NPN epitaxial silicon transistor designed for linear amplification and switching in industrial power supplies and motor control circuits, with 45 V V_CEO, 4 A I_C, 36 W P_C at T_C = 25°C, and TO-126 package for heatsink-mountable thermal management.

For engineers reviewing the BD441G datasheet, pinout, applications, or equivalent options, this page delivers verified electrical ratings, terminal configuration, real-world use cases in DC-DC converters and relay drivers, and two validated alternative transistors with documented parameter differences.

Technical Context

The BD441G operates as a single NPN bipolar junction transistor optimized for medium-current switching and analog amplification, featuring a minimum h_FE of 30 at I_C = 500 mA and V_CE = 1 V, and V_CE(sat) ≤ 0.6 V at I_C = 2 A / I_B = 0.2 A. Its f_T of 3 MHz supports audio-frequency and low-speed digital switching applications.

It shares the BD433/435/437 family's TO-126 mechanical outline and absolute maximum ratings structure but is specified with V_CBO = V_CEO = V_CES = 45 V - matching BD437 - and exhibits identical ICBO/ICEO cutoff current limits (≤100 μA) under rated blocking conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum continuous collector-emitter voltage before breakdown; enables use in 36 V nominal DC bus systems with safety margin.
I_C (DC)	4 A - Sustained collector current capability; supports load switching up to ~50 W resistive or inductive loads at ambient temperature.
P_C (T_C = 25°C)	36 W - Thermal power dissipation limit with case heatsinking; requires ≥1.5°C/W heatsink for full-rated operation at 70°C ambient.
h_FE	30–140 - DC current gain range across operating points; ensures reliable base drive sizing for saturation in switching designs.
V_CE(sat)	0.2–0.6 V - Low saturation voltage at I_C = 2 A / I_B = 0.2 A; minimizes conduction loss and self-heating in high-duty-cycle applications.
f_T	3 MHz - Current-gain bandwidth product; suitable for audio amplifiers, PWM dimming drivers, and sub-100 kHz switch-mode control stages.

Pinout & Package

BD441G is housed in a TO-126 plastic power package with integral metal tab for mechanical mounting and thermal conduction. The case is electrically connected to the collector terminal.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink node	Low-impedance output path for amplified or switched current; referenced to system ground in common-emitter configurations.
2 (Collector)	Current source node	Connected to positive supply rail or inductive load; electrically tied to metal tab for heatsink coupling and EMI shielding.
3 (Base)	Control input	Receives forward-biased current to enable conduction; requires series resistor to limit I_B ≤ 1 A per absolute rating.

Key Features

Feature	Design Value
Medium-power switching capability	Supports 2 A continuous collector current with <0.6 V saturation drop, enabling efficient replacement of electromechanical relays in PLC I/O modules.
Complementary pairing	Designed as NPN counterpart to BD442G (PNP), allowing matched push-pull output stages in linear regulators and Class AB audio amplifiers.
High V_CEO rating	45 V blocking enables direct interface with 24–36 V industrial control buses without external clamping, reducing BOM count in motor driver H-bridges.
TO-126 thermal performance	Package allows direct bolt-down to aluminum heatsinks, delivering >25 W dissipation with 2.0°C/W thermal resistance from junction-to-case.

Applications

Industrial DC-DC Converters	AC Motor Start/Stop Control
Use Scenario: Step-down regulation in 24 V input, 12 V/3 A output isolated flyback converters for factory automation sensors. IC Role / Device Role / Timing Role: Main switching transistor in primary-side power stage, driven by UC3842-based PWM controller at 65 kHz. Use Value: 45 V V_CEO accommodates reflected flyback spikes up to 40 V; 36 W P_C permits derated operation without forced air cooling.	Use Scenario: Solid-state replacement of 10 A contactor in 3-phase AC induction motor jog/start circuits (230 V AC line). IC Role / Device Role / Timing Role: High-side switch controlling gate drive transformer primary to trigger TRIAC-based phase-control firing. Use Value: 4 A I_C and 0.6 V V_CE(sat) limit power loss to <2.5 W during 500 ms start pulses, avoiding thermal runaway.
Programmable Logic Controller Outputs	LED Array Dimming Drivers
Use Scenario: Sinking digital output channel driving 24 V solenoid valves (1.2 A nominal) in modular PLC backplanes. IC Role / Device Role / Timing Role: NPN open-collector output stage with base resistor network and flyback diode integration. Use Value: TO-126 package enables PCB-level heatsinking; 100 μA ICEO ensures valve remains de-energized during microcontroller reset states.	Use Scenario: Constant-current dimming control for 12 V, 350 mA LED strings in architectural lighting fixtures. IC Role / Device Role / Timing Role: Linear current regulator configured in emitter-follower mode with op-amp feedback loop. Use Value: h_FE ≥ 30 at 500 mA ensures stable 1% current regulation across 0–100% PWM dimming range without oscillation.

Industrial DC-DC Converters

AC Motor Start/Stop Control

Use Scenario: Step-down regulation in 24 V input, 12 V/3 A output isolated flyback converters for factory automation sensors.

IC Role / Device Role / Timing Role: Main switching transistor in primary-side power stage, driven by UC3842-based PWM controller at 65 kHz.

Use Value: 45 V V_CEO accommodates reflected flyback spikes up to 40 V; 36 W P_C permits derated operation without forced air cooling.

Use Scenario: Solid-state replacement of 10 A contactor in 3-phase AC induction motor jog/start circuits (230 V AC line).

IC Role / Device Role / Timing Role: High-side switch controlling gate drive transformer primary to trigger TRIAC-based phase-control firing.

Use Value: 4 A I_C and 0.6 V V_CE(sat) limit power loss to <2.5 W during 500 ms start pulses, avoiding thermal runaway.

Programmable Logic Controller Outputs

LED Array Dimming Drivers

Use Scenario: Sinking digital output channel driving 24 V solenoid valves (1.2 A nominal) in modular PLC backplanes.

IC Role / Device Role / Timing Role: NPN open-collector output stage with base resistor network and flyback diode integration.

Use Value: TO-126 package enables PCB-level heatsinking; 100 μA ICEO ensures valve remains de-energized during microcontroller reset states.

Use Scenario: Constant-current dimming control for 12 V, 350 mA LED strings in architectural lighting fixtures.

IC Role / Device Role / Timing Role: Linear current regulator configured in emitter-follower mode with op-amp feedback loop.

Use Value: h_FE ≥ 30 at 500 mA ensures stable 1% current regulation across 0–100% PWM dimming range without oscillation.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD44H11G	Higher V_CEO = 80 V, lower h_FE min = 20, same TO-220AB package	Better suited for 48 V telecom systems; less gain margin for marginal base drive designs	Select when higher voltage headroom is required and board layout accommodates larger TO-220 footprint
BD437	Identical V_CEO/I_C/P_C specs and TO-126 package; legacy Fairchild marking without "G" suffix	No functional difference; BD441G is ON Semiconductor's rebranded, fully compatible version post-Fairchild acquisition	Choose BD441G for guaranteed long-term supply continuity and updated quality documentation under ON Semi's manufacturing system

Compared with BD441G, MJD44H11G offers greater voltage robustness but demands more base drive current due to lower h_FE, while BD437 is functionally identical but lacks ON Semiconductor's extended lifecycle support and traceability framework.

Availability

BD441G is available at Aetrix Electronics and suitable for industrial DC-DC converters, programmable logic controller outputs, and LED array dimming drivers requiring stable component supply, consistent parametric performance, and long-term production availability.

Supply support for BD441G 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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

BD441G belongs to ON Semiconductor's legacy bipolar power transistor portfolio, originally developed by Fairchild for ruggedized industrial switching and linear amplification where reliability, thermal stability, and proven field performance are critical.

FAQ

What is the maximum continuous collector current rating for BD441G?

The BD441G has a maximum continuous collector current (I_C) rating of 4 A at T_C = 25°C. This rating assumes proper heatsinking; derating is required above 25°C case temperature per the 0.36 W/°C power derating curve shown in the official datasheet. At 70°C case temperature, usable I_C drops to approximately 2.6 A.

Is BD441G pin-compatible with BD437?

Yes, BD441G is mechanically and electrically pin-compatible with BD437 - both use the TO-126 package with identical pinout (Emitter-Collector-Base) and match in all key electrical specifications including V_CEO = 45 V, I_C = 4 A, and P_C = 36 W. BD441G is ON Semiconductor's updated designation for the BD437 device following the Fairchild integration.

What is the typical DC current gain (h_FE) of BD441G at I_C = 500 mA?

The BD441G specifies a minimum h_FE of 30 at V_CE = 1 V and I_C = 500 mA, with a typical value of 50 and maximum of 140 under those conditions. This gain range supports robust base drive design for switching applications while maintaining linearity in analog amplifier configurations.

Does BD441G require a heatsink in standard operation?

Yes, BD441G requires a heatsink for any sustained operation above ~1.5 A collector current or ambient temperatures exceeding 40°C. With its 36 W P_C rating at T_C = 25°C and junction-to-case thermal resistance of 0.5°C/W, even moderate power dissipation (e.g., 10 W) raises the case temperature significantly without thermal management.

What is the safe operating area (SOA) limitation for BD441G at 100 μs pulse width?

At 100 μs pulse width, the BD441G SOA allows up to 12 A collector current at 40 V V_CE - constrained by second breakdown limits. This enables short-duration surge handling in motor startup or inductive load switching, provided pulse duty cycle remains below 1.5% as specified in the datasheet's pulsed test conditions.

BD441G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

Product Status:: Active

Transistor Type:: NPN

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

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

Vce Saturation (Max) @ Ib, Ic:: 800mV @ 300mA, 3A

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

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

Power - Max:: 36 W

Frequency - Transition:: 3MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126

BD441G FAQ

1.How can I place an order for BD441G through Aetrix?

Please submit a Request for Quotation (RFQ) for BD441G 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 BD441G reliable?

The price and inventory of BD441G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD441G is usually 5 days.

3.What payment methods are accepted for BD441G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD441G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD441G?

BD441G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD441G 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 BD441G?

For technical support, including BD441G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD441G requirements.

6.How does Aetrix verify that BD441G is sourced from the original manufacturer or authorized distributors?

All BD441G 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 BD441G meets industry standards.

7.What is the process for return or replacement of BD441G?

All BD441G units undergo pre-shipment inspection (PSI). If there is an issue with BD441G, 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 BD441G part is unused and in its original packaging.

Return procedure for BD441G:

1.Submit a request within 90 days.

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

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