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

STMicroelectronics BUT90

Name: BUT90
Brand: STMicroelectronics
SKU: BUT90
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUT90

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: BUT90.pdf

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

Quantity:: RFQ Add To RFQ list

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Inventory:9,332

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Product details

Overview

BUT90 from STMicroelectronics is a high-power NPN silicon transistor in TO-3 package, designed for high-current switching and linear amplification in industrial power systems. It delivers 50 A continuous collector current, 200 V collector-emitter blocking voltage (V_CEV), and 0.55 V typical V_CE(sat) at 35 A/1.75 A drive - enabling efficient motor control and UPS inverters.

For engineers reviewing the BUT90 datasheet, BUT90 pinout, BUT90 application, or BUT90 equivalent, key selection criteria include ruggedness under inductive switching (120 A peak I_C), thermal resistance (0.7 °C/W junction-to-case), and fast turn-off (0.2–0.4 µs fall time) in high-reliability 100 V, 70 A switching loads.

Technical Context

The BUT90 employs multiepitaxial planar construction to support high-voltage blocking (125 V V_CEO) and high-current conduction (50 A I_C) with low saturation voltage. Its rugged design tolerates repetitive inductive energy dissipation, evidenced by 125 V sustaining voltage (V_CEO(sus)) at 0.2 A with 25 mH load and 1.25–2 µs storage time under clamped inductive switching.

Thermal performance is defined by a maximum junction temperature of 200 °C and 0.7 °C/W R_thj-case, requiring direct mounting to heatsinks. Electrical behavior is specified at case temperature (not ambient), with saturation voltages and switching times validated at T_c = 25 °C and T_c = 100 °C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEV	200 V - Enables operation in 100–160 V DC bus applications with 2× safety margin against transients
I_C	50 A continuous - Supports high-power motor drives and UPS output stages without parallel devices
V_CE(sat)	0.55 V typ. @ 35 A/1.75 A - Limits conduction loss to ≤19 W at rated current, reducing heatsink requirements
t_f	0.2–0.4 µs - Ensures clean turn-off in 100 kHz-class switch-mode converters with minimal tail current
R_thj-case	0.7 °C/W - Allows 250 W dissipation with ≤175 °C junction rise above 25 °C case, compatible with standard TO-3 heatsinks
T_{j max}	200 °C - Permits sustained operation in sealed industrial enclosures with elevated ambient temperatures

Pinout & Package

TO-3 (version "S") metal-can package with isolated collector tab; requires electrically insulating mounting hardware. Pin configuration: Pin 1 = Base, Pin 2 = Collector (case-connected), Pin 3 = Emitter.

Pin/Terminal	Circuit Role	Design Meaning
Base (Pin 1)	Control input	Receives 1.75–7 A drive current to saturate transistor; low V_BE(sat) (1.0–1.45 V) reduces driver power loss
Collector (Pin 2 / Case)	High-current output node	Electrically connected to metal case; must be insulated from heatsink unless system ground reference permits
Emitter (Pin 3)	Power return path	Carries full load current; low-inductance layout critical to minimize switching overshoot in inductive loads

Key Features

Feature	Design Value
High ruggedness rating	Withstands 125 V sustaining voltage at 0.2 A with 25 mH inductive load - prevents secondary breakdown during motor stall or short-circuit events
Fast switching speed	0.8–1.6 µs rise time and 0.16–0.5 µs fall time (inductive) enable >100 kHz operation with low switching loss
Low saturation voltage	0.55 V typical V_CE(sat) at 35 A reduces conduction loss by ~35% vs. legacy 1 V-sat transistors at same current
High junction temperature rating	200 °C max T_j allows derated operation in compact, convection-cooled industrial enclosures up to 90 °C ambient

Applications

Uninterruptible Power Supply (UPS)

Motor Control

Use Scenario: Bidirectional DC-AC inverter stage in line-interactive UPS delivering 1–3 kVA output.

IC Role / Device Role / Timing Role: Main switching device in half-bridge output stage, commutating 70 A peak inductive current at 10–20 kHz.

Use Value: Low V_CE(sat) and fast t_f reduce total losses by ≥18 W per device vs. older 2N3055 derivatives, improving efficiency from 89% to 91.5% at full load.

Use Scenario: High-current H-bridge driver for 3-phase BLDC compressor in HVAC systems.

IC Role / Device Role / Timing Role: Low-side switching element handling 50 A continuous current with PWM frequencies up to 15 kHz.

Use Value: 0.7 °C/W thermal resistance enables direct mounting to chassis without forced air, cutting BOM cost by eliminating dedicated heatsinks and fans.

Switching Regulator

Industrial Linear Amplifier

Use Scenario: Primary-side switch in 500 W forward converter for industrial PLC power supply.

IC Role / Device Role / Timing Role: High-voltage, high-current switch operating at 100 kHz with 100 V DC input and 200 V transient tolerance.

Use Value: 200 V V_CEV rating eliminates need for snubber networks in 100 V bus designs, simplifying PCB layout and improving reliability.

Use Scenario: Class-AB linear output stage in precision DC servo amplifier for CNC motion control.

IC Role / Device Role / Timing Role: High-fidelity current gain element delivering 40 A continuous output with <1% THD at 1 kHz.

Use Value: Multiepitaxial planar structure ensures stable h_FE > 15 across 0.1–50 A, enabling predictable biasing and thermal tracking in push-pull configurations.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU2508DX	Lower V_CEV (160 V), higher R_thj-case (0.9 °C/W), slower t_f (0.6 µs)	Limited to ≤80 V DC bus; requires larger heatsink for same power dissipation	Acceptable where 160 V rating suffices and space allows extra thermal margin
2SD3152	Higher V_CEV (250 V), but lower I_C (30 A), no published inductive switching data	Suitable for higher-voltage flyback converters but not for 50 A motor drive loads	Preferred only when >200 V blocking is mandatory and current demand is ≤30 A

Compared with BU2508DX and 2SD3152, the BUT90 uniquely balances 200 V blocking, 50 A current, and sub-microsecond switching - making it optimal for 100 V-class industrial inverters where both voltage headroom and thermal density matter.

Availability

BUT90 is available at Aetrix Electronics and suitable for uninterruptible power supply, motor control, and switching regulator applications requiring stable component supply and long-lifecycle industrial support.

Supply support for BUT90 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 automotive ICs.

The BUT90 belongs to ST's high-power bipolar transistor product line, engineered specifically for ruggedized industrial switching and linear amplification where reliability under repetitive overloads and high junction temperatures is non-negotiable.

FAQ

Is BUT90 still in active production?

No - the BUT90 is marked "Obsolete Product(s)" in its official STMicroelectronics datasheet (Rev. 4, Feb 2003). However, Aetrix Electronics maintains legacy inventory with full traceability and supports design-in through remaining stock and cross-reference guidance for functionally aligned replacements.

What is the recommended base drive circuit for BUT90 in switching applications?

For reliable saturation at 35 A collector current, apply 1.75 A DC base current via a low-impedance driver (e.g., complementary Darlington or gate driver IC with ≥2 A peak output). Use a 10 Ω base resistor in series with a 100 nF capacitor to suppress ringing, and ensure base-emitter reverse bias (−1.5 V) during turn-off to minimize storage time.

Can BUT90 be used in parallel configurations?

Yes - BUT90 exhibits positive thermal coefficient of V_CE(sat), enabling inherent current sharing. For parallel operation, use matched devices (within 5% V_CE(sat)), individual base resistors (≤1 Ω), and symmetrical PCB layout with Kelvin emitter connections to avoid circulating currents.

Does BUT90 require a heatsink, and what mounting torque is specified?

Yes - due to 250 W P_tot, a heatsink is mandatory. ST specifies 1.7–2.0 N·m mounting torque for the TO-3 screw. Use mica or silicone washer insulation with thermal grease (0.1 mm thickness, κ ≥ 1.5 W/m·K) to maintain R_thj-case ≤ 0.7 °C/W while ensuring electrical isolation.

BUT90 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 @ 7A, 70A

Current - Collector Cutoff (Max):: -

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

Power - Max:: 250 W

Frequency - Transition:: -

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Chassis Mount

Supplier Device Package:: TO-3

BUT90 FAQ

1.How can I place an order for BUT90 through Aetrix?

Please submit a Request for Quotation (RFQ) for BUT90 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 BUT90 reliable?

The price and inventory of BUT90 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUT90 is usually 5 days.

3.What payment methods are accepted for BUT90?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUT90 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUT90?

BUT90 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUT90 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 BUT90?

For technical support, including BUT90 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUT90 requirements.

6.How does Aetrix verify that BUT90 is sourced from the original manufacturer or authorized distributors?

All BUT90 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 BUT90 meets industry standards.

7.What is the process for return or replacement of BUT90?

All BUT90 units undergo pre-shipment inspection (PSI). If there is an issue with BUT90, 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 BUT90 part is unused and in its original packaging.

Return procedure for BUT90:

1.Submit a request within 90 days.

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

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