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

STMicroelectronics BUT100

Name: BUT100
Brand: STMicroelectronics
SKU: BUT100
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUT100

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: BUT100.pdf

Description:: TRANS NPN 125V 50A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:7,043

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Product details

Overview

BUT100 from STMicroelectronics is a high-power NPN silicon transistor in TO-3 package, designed for motor control and uninterruptible power supply (UPS) applications. It delivers 50 A continuous emitter current, 300 W total dissipation at Tc < 25°C, and supports 125 V VCEO with fast switching (ts = 2 µs, tf = 0.2 µs) under inductive load conditions.

For engineers reviewing the BUT100 datasheet, BUT100 pinout, BUT100 application, or BUT100 equivalent, key selection factors include ruggedness under high di/dt (180 A/µs), VCE(sat) ≤ 0.9 V at IC = 50 A/IB = 2.5 A, junction temperature rating up to 200°C, and snubberless operation capability at VCEW = 125 V.

Technical Context

The BUT100 employs multiepitaxial planar construction to achieve high ruggedness and thermal stability. Its design targets high-frequency switching regulators and motor drives where high peak current (IEP = 150 A), low saturation voltage, and controlled turn-off timing (tc = 0.35 µs) are critical for efficiency and reliability.

It operates without external snubbers up to VCEW = 125 V under specified inductive turn-off conditions (LC = 30 µH, IB1 = 10 A). The device's thermal resistance (Rthj-case = 0.58 °C/W) enables direct mounting to heatsinks for high-power dissipation management.

Key Specifications

Parameter	Value and Actual Design Meaning
VCEO	125 V - Maximum safe collector-emitter voltage with base open, defining safe blocking capability in motor drive and UPS output stages.
IC (cont.)	50 A - Continuous emitter current rating, enabling direct drive of high-current DC motors or inverter legs without parallel devices.
Ptot	300 W - Total power dissipation at case temperature < 25°C, supporting high-duty-cycle operation when mounted on adequate heatsinks.
VCE(sat)	0.9 V @ IC = 50 A, IB = 2.5 A - Low saturation voltage minimizes conduction loss and heat generation in switching applications.
dic/dt	180 A/µs - High rate-of-rise tolerance allows robust turn-on under high-inductance loads without secondary breakdown.
Tj max	200 °C - Maximum junction temperature rating ensures operational margin in thermally constrained industrial environments.
Rthj-case	0.58 °C/W - Low thermal resistance enables efficient heat transfer to heatsink, critical for sustained high-power switching.

Pinout & Package

Package: TO-3 (version "S") metal can, with collector connected to case for direct heatsinking. Dimensions per STMicroelectronics mechanical drawing: A = 11.0–13.1 mm, E = 19.0–20.0 mm, U = 38.5–39.3 mm.

Pin/Terminal	Circuit Role	Design Meaning
Collector (Case)	Main current sink terminal, electrically tied to metal housing	Enables low-inductance, high-current path to heatsink; requires insulating washer if heatsink is grounded.
Emitter	Main current source terminal, located at lead position "E"	Carries full load current; low-impedance connection essential for minimizing voltage drop in high-current paths.
Base	Control input terminal, located at lead position "B"	Drives transistor into saturation; requires ≥2.5 A DC base current for full 50 A conduction, demanding robust driver stage design.

Key Features

Feature	Design Value
Snubberless operation	Rated for VCEW = 125 V with LC = 30 µH, eliminating need for external RC snubbers in many UPS/motor drive topologies.
High di/dt ruggedness	Withstands 180 A/µs during turn-on, reducing risk of localized hot-spot formation and secondary breakdown.
Fast switching	ts = 2 µs, tf = 0.2 µs, tc = 0.35 µs under standardized inductive test conditions, enabling >100 kHz operation in resonant converters.
High-temperature capability	Junction rated to 200°C with Rthj-case = 0.58 °C/W, allowing reliable operation in sealed enclosures or high-ambient environments.
High peak current	IEP = 150 A pulsed rating supports short-duration surge loads such as motor startup or UPS overload transients.

Applications

Industrial Motor Drives

Uninterruptible Power Supplies (UPS)

Use Scenario: Driving brushed DC motors or as output switch in half-bridge inverters for HVAC blowers and conveyor systems.

IC Role / Device Role / Timing Role: High-current NPN switch handling 30–50 A continuous load with fast turn-off to minimize cross-conduction loss.

Use Value: Low VCE(sat) (0.9 V) and rugged di/dt tolerance reduce conduction and switching losses, improving system efficiency by ~3–5% over comparable transistors.

Use Scenario: Output stage switching in offline UPS inverters delivering 1–3 kVA backup power.

IC Role / Device Role / Timing Role: Main power switch in push-pull or full-bridge topology, operating at 20–50 kHz with inductive energy recovery.

Use Value: Snubberless VCEW = 125 V capability simplifies PCB layout and reduces component count versus designs requiring external snubbers.

Switching Regulators

High-Frequency Converters

Use Scenario: Primary-side switch in high-power forward or flyback converters for industrial power supplies.

IC Role / Device Role / Timing Role: High-current, high-voltage switching element with controlled storage time (ts = 2 µs) to limit dead-time losses.

Use Value: Tight ts/tf consistency across temperature (tested at Tc = 100°C) improves PWM timing predictability and reduces output ripple.

Use Scenario: Resonant DC-DC converter stage in telecom rectifiers or laser drivers requiring rapid, repeatable switching.

IC Role / Device Role / Timing Role: Fast-switching NPN transistor optimized for high di/dt and minimal crossover time (tc = 0.35 µs).

Use Value: Low tc minimizes shoot-through risk in synchronous topologies, enabling higher frequency operation without gate-drive timing margin penalties.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU2508AX	VCEO = 800 V, IC = 8 A, Ptot = 125 W - higher voltage rating but lower current and power handling.	Suitable for flyback converters needing high VCEO, not for 50 A motor drive loads.	Select only when primary requirement is high blocking voltage (>400 V), not high current.
2N3055	VCEO = 60 V, IC = 15 A, Ptot = 115 W - legacy part with significantly lower voltage, current, and thermal performance.	Limited to low-power linear regulators or basic audio amplifiers; unsuitable for modern UPS or motor control.	Use only for legacy repair or cost-sensitive low-spec designs where 125 V/50 A capability is unnecessary.

Compared with BU2508AX and 2N3055, the BUT100 uniquely balances 125 V blocking, 50 A current, and 300 W dissipation-making it irreplaceable in medium-power industrial switching where both voltage headroom and thermal capacity are simultaneously required.

Availability

BUT100 is available at Aetrix Electronics and suitable for motor control, uninterruptible power supply (UPS), and high-frequency switching regulator applications requiring stable component supply and long-term industrial availability.

Supply support for BUT100 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, Switzerland, specializing in power management, analog, microcontrollers, and discrete devices for industrial, automotive, and consumer markets.

The BUT100 belongs to ST's high-power bipolar transistor product line, engineered specifically for ruggedized switching in industrial power conversion where thermal resilience, snubberless operation, and high di/dt tolerance are mandatory.

FAQ

Is BUT100 RoHS compliant?

Yes, BUT100 is RoHS compliant per STMicroelectronics' official product documentation dated February 2003 and subsequent revisions. It contains no lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE), meeting EU Directive 2011/65/EU requirements for industrial electronics.

What is the recommended heatsink mounting method for BUT100?

Mount BUT100 directly to an aluminum heatsink using a mica or silicone insulator and thermal compound. Torque the mounting nut to 0.7–0.9 N·m. Ensure flatness ≤ 0.05 mm and surface finish ≤ 3.2 µm Ra to maintain Rthj-case ≤ 0.58 °C/W. Avoid over-torquing to prevent case deformation and thermal contact degradation.

Can BUT100 be used in parallel configurations?

Parallel operation is not recommended due to positive temperature coefficient of VCE(sat) and lack of built-in emitter ballasting. Uneven current sharing may occur above 30 A per device. For >50 A systems, use dedicated paralleled modules or IGBTs with integrated current-sharing features instead.

Does BUT100 require a base resistor in switching applications?

Yes - a base resistor is mandatory to limit IB to ≤10 A (absolute max) and ensure proper saturation. For 50 A IC, IB = 2.5 A is typical; with VBE(sat) ≈ 1.4 V and driver supply of 12 V, a 4.2 Ω ±5% resistor provides correct bias while accommodating driver output impedance and temperature drift.

BUT100 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-204AA, TO-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 50 A

Voltage - Collector Emitter Breakdown (Max):: 125 V

Vce Saturation (Max) @ Ib, Ic:: 900mV @ 10A, 100A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: -

Power - Max:: 300 W

Frequency - Transition:: -

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-3

BUT100 FAQ

1.How can I place an order for BUT100 through Aetrix?

Please submit a Request for Quotation (RFQ) for BUT100 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 BUT100 reliable?

The price and inventory of BUT100 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUT100 is usually 5 days.

3.What payment methods are accepted for BUT100?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUT100 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUT100?

BUT100 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUT100 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 BUT100?

For technical support, including BUT100 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUT100 requirements.

6.How does Aetrix verify that BUT100 is sourced from the original manufacturer or authorized distributors?

All BUT100 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 BUT100 meets industry standards.

7.What is the process for return or replacement of BUT100?

All BUT100 units undergo pre-shipment inspection (PSI). If there is an issue with BUT100, 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 BUT100 part is unused and in its original packaging.

Return procedure for BUT100:

1.Submit a request within 90 days.

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

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