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

STMicroelectronics BUX48A

Name: BUX48A
Brand: STMicroelectronics
SKU: BUX48A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUX48A

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: BUX48A.pdf

Description:: TRANS NPN 450V 15A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:2,775

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Product details

Overview

BUX48A from STMicroelectronics is a high-voltage, high-current NPN silicon power transistor in TO-3 metal package, rated for V_CEO = 450 V, I_C = 15 A, and P_tot = 175 W at T_c = 25 °C. It delivers fast switching (t_s = 3 µs, t_f = 0.8 µs under resistive load) and is engineered for primary-side switching in flyback and forward SMPS operating directly from single-phase mains.

For engineers reviewing the BUX48A datasheet, BUX48A pinout, BUX48A application, or BUX48A equivalent, key selection criteria include its 450 V V_CEO, 15 A continuous collector current, TO-3 thermal resistance of 1 °C/W, and validated inductive switching performance at 300 V with 3 µH load - critical for offline AC/DC converter reliability and efficiency.

Technical Context

This device uses multiepitaxial mesa construction to achieve high breakdown voltage while maintaining low saturation voltage (V_CE(sat) = 1.5 V @ I_C = 12 A, I_B = 2.4 A) and robust secondary breakdown immunity. Its base-emitter junction supports V_EBO = 7 V and I_B = 4 A continuous drive capability.

The BUX48A is optimized for hard-switched, non-resonant topologies: it specifies storage time (t_s) and fall time (t_f) under both resistive (150 V) and inductive (300 V, 3 µH) conditions, with guaranteed t_f ≤ 0.4 µs at 125 °C - enabling stable operation in high-frequency, high-voltage SMPS designs.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	450 V - Sustains full mains-derived DC bus (e.g., ~325 V after rectification) with margin for line surges and ringing in flyback converters.
I_C	15 A - Supports output power up to ~250 W in single-transistor forward converters with adequate heatsinking.
P_tot @ T_c = 25 °C	175 W - Enables high-power density when mounted on large aluminum heatsinks with low thermal interface resistance.
R_thj-case	1 °C/W - Allows junction temperature rise of only 100 °C at 100 W dissipation, supporting reliable 200 °C max T_j operation.
t_f (inductive)	0.4 µs @ 300 V, 125 °C - Limits switching loss during turn-off in high-voltage inductive loads, improving efficiency above 50 kHz.
V_CE(sat)	1.5 V @ I_C = 12 A, I_B = 2.4 A - Reduces conduction loss to <18 W at full load, easing thermal design vs. higher-V_CE(sat) alternatives.

Pinout & Package

Package: TO-3 metal case (case temperature referenced), with electrically isolated collector tab (pin 2), emitter (pin 1), and base (pin 3) - standard three-terminal configuration for high-power discrete mounting.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Main current return path; connected to ground or low-side reference; requires low-inductance layout to minimize switching oscillation.
2	Collector (Tab)	Electrically isolated metal tab carrying full switched current; must be mounted to heatsink with insulating washer and thermal paste.
3	Base	Current-controlled input; requires ≥2.4 A peak drive for full saturation at 12 A collector current; sensitive to ESD and overvoltage.

Key Features

Feature	Design Value
Multiepitaxial mesa structure	Enables simultaneous high V_CEO (450 V) and low V_CE(sat) (1.5 V), reducing trade-off between blocking voltage and conduction loss.
200 °C maximum junction temperature	Permits operation in high-ambient industrial environments (e.g., enclosed power supplies) without derating below 150 °C ambient.
Guaranteed inductive switching times	t_s ≤ 5 µs and t_f ≤ 0.4 µs at 125 °C confirm stable hard-switching behavior in real-world transformer-coupled circuits.
TO-3 package with 1 °C/W R_thj-case	Supports direct bolt-down heatsinking for high-reliability, long-lifetime power stages where plastic packages would thermally saturate.

Applications

Offline Flyback SMPS

Single-Transistor Forward Converter

Use Scenario: 100–250 W AC/DC adapter converting universal input (85–265 VAC) to isolated 12–24 VDC using self-oscillating or PWM-controlled flyback topology.

IC Role / Device Role / Timing Role: Primary-side main switch handling full DC bus voltage and peak current during energy transfer phase.

Use Value: 450 V V_CEO provides 38% margin over 325 V rectified peak, while 1.5 V V_CE(sat) limits conduction loss to <18 W at 12 A, improving light-load efficiency.

Use Scenario: Industrial 200 W DC/DC module accepting 375 VDC input (PFC output) and delivering regulated 48 VDC with synchronous rectification.

IC Role / Device Role / Timing Role: Main power switch in single-ended forward topology, conducting during transformer reset interval and requiring robust SOA.

Use Value: 15 A I_C and 175 W P_tot support high-duty-cycle operation; 200 °C T_j(max) ensures stability under sustained overload conditions.

AC Motor Start Assist

Mains-Fed Induction Heater Driver

Use Scenario: Solid-state relay replacement in HVAC compressor start circuits, switching 240 VAC/15 A resistive-inductive loads for <5 s durations.

IC Role / Device Role / Timing Role: High-current, high-voltage switch triggered by microcontroller to energize start winding.

Use Value: 55 A I_CP non-repetitive rating handles motor inrush; TO-3 mechanical robustness withstands repeated thermal cycling better than plastic-packaged alternatives.

Use Scenario: Half-bridge driver stage in 1–3 kW induction heating system operating from 230 VAC mains with resonant tank.

IC Role / Device Role / Timing Role: Single-transistor switch in asymmetrical half-bridge configuration driving series-resonant LC load.

Use Value: Verified t_f ≤ 0.4 µs at 300 V enables clean zero-voltage switching transitions; 1 °C/W thermal resistance maintains safe T_j under burst-mode operation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BUV48A	Same die, TO-218 plastic package; R_thj-case = 1.2 °C/W; V_CEO = 450 V; I_C = 15 A; P_tot = 125 W.	Limited to lower-power (<150 W) or forced-air-cooled designs due to reduced power dissipation and higher thermal resistance.	Select when cost-sensitive, space-constrained, or non-isolated mounting is acceptable - avoid in sealed enclosures or >100 W continuous operation.
BUV48AFI	Same die, ISOWATT218 fully isolated package; R_thj-case = 2.2 °C/W; V_CEO = 450 V; I_C = 15 A; P_tot = 55 W.	Suitable only for low-duty-cycle or pulsed applications (e.g., ignition coils) due to 55 W power limit and doubled thermal resistance.	Choose only when electrical isolation between collector and heatsink is mandatory and average power remains <30 W - not for SMPS primary switches.

Compared with BUX48A, BUV48A trades thermal performance for lower cost and smaller footprint, while BUV48AFI sacrifices power handling for galvanic isolation - making BUX48A the sole choice for high-reliability, high-power, air-cooled offline SMPS primary-side switching.

Availability

BUX48A is available at Aetrix Electronics and suitable for offline AC/DC power supplies, industrial motor control interfaces, and high-voltage pulse generators requiring stable component supply across extended production lifecycles.

Supply support for BUX48A 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 automotive, industrial, and consumer markets.

The BUX48A belongs to ST's high-voltage bipolar power transistor product line, developed specifically for ruggedized, mains-connected switching applications demanding high SOA, fast switching, and long-term thermal reliability.

FAQ

Is BUX48A pin-compatible with BUX48?

Yes - BUX48A and BUX48 share identical TO-3 pinout (emitter-base-collector on pins 1-3) and mechanical dimensions. However, BUX48A features improved V_CEO (450 V vs. 400 V), higher I_C (15 A vs. 15 A same, but tighter spec), and enhanced inductive switching specs at elevated temperature, making it a direct upgrade.

What is the recommended base drive for reliable saturation?

A minimum base current of 2.4 A is required to fully saturate BUX48A at I_C = 12 A (per datasheet test condition). Use a low-impedance driver (e.g., complementary Darlington or gate driver IC with ≥3 A peak output) and keep base trace short and wide to minimize inductance and prevent switching oscillation.

Can BUX48A be used in avalanche mode?

No - BUX48A is not rated or characterized for repetitive avalanche operation. Its SOA curve defines safe operating area only under clamped inductive switching. For unclamped inductive loads, external snubbers or clamping circuits must limit V_CE to ≤450 V to prevent destructive breakdown.

Does the TO-3 package require an insulating mounting kit?

Yes - although the collector tab is electrically isolated per datasheet, ST recommends using an insulating washer (e.g., mica or silicone pad) plus thermal compound when mounting to grounded heatsinks. This prevents unintended collector-to-chassis shorts and maintains creepage/clearance compliance in safety-certified designs.

BUX48A Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tray

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 15 A

Voltage - Collector Emitter Breakdown (Max):: 450 V

Vce Saturation (Max) @ Ib, Ic:: 5V @ 2.4A, 12A

Current - Collector Cutoff (Max):: 200µA

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

Power - Max:: 175 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Chassis Mount

Supplier Device Package:: TO-3

BUX48A FAQ

1.How can I place an order for BUX48A through Aetrix?

Please submit a Request for Quotation (RFQ) for BUX48A 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 BUX48A reliable?

The price and inventory of BUX48A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUX48A is usually 5 days.

3.What payment methods are accepted for BUX48A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUX48A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUX48A?

BUX48A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUX48A 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 BUX48A?

For technical support, including BUX48A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUX48A requirements.

6.How does Aetrix verify that BUX48A is sourced from the original manufacturer or authorized distributors?

All BUX48A 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 BUX48A meets industry standards.

7.What is the process for return or replacement of BUX48A?

All BUX48A units undergo pre-shipment inspection (PSI). If there is an issue with BUX48A, 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 BUX48A part is unused and in its original packaging.

Return procedure for BUX48A:

1.Submit a request within 90 days.

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

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