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

STMicroelectronics BULD741T4

Name: BULD741T4
Brand: STMicroelectronics
SKU: BULD741T4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BULD741T4

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Datasheet:: BULD741T4.pdf

Description:: TRANS NPN 400V 2.5A DPAK

Quantity:: RFQ Add To RFQ list

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Inventory:7,419

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Product details

Overview

BULD741T4 from STMicroelectronics is a high-voltage fast-switching NPN power transistor in DPAK (TO-252) package, rated for V_CEO = 400 V, I_C = 2.5 A, and P_TOT = 30 W at T_C = 25 °C. It delivers V_CEO(sus) = 450 V sustaining voltage, t_s = 3.5 µs storage time, and 5 mJ repetitive avalanche energy, enabling robust operation in electronic ballasts and SMPS without external Transil protection.

For engineers reviewing the BULD741T4 datasheet, BULD741T4 pinout, BULD741T4 application, or BULD741T4 equivalent, key selection criteria include high-voltage ruggedness (V_CES = 1050 V), low saturation voltage (V_CE(sat) = 0.5 V @ I_C = 2 A), fast switching (t_f = 500 ns), thermal resistance (R_thJC = 4.16 °C/W), and intrinsic avalanche capability.

Technical Context

This device uses high-voltage multi-epitaxial planar technology with an enhanced intermediate layer to improve breakdown ruggedness and switching speed. Its design enables safe operation under high collector current during breakdown-eliminating need for external Transil clamping in lamp ballast converters.

The transistor supports resistive-load switching with t_s = 3.5 µs and t_f = 500 ns at h_FE = 5–10, and sustains 450 V at I_C = 10 mA with zero base current. Its R_thJC = 4.16 °C/W and T_J(max) = 150 °C support thermally demanding power stage layouts.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - Maximum collector-emitter voltage with base open; defines safe operating ceiling in flyback and resonant converters
V_CES	1050 V - Collector-emitter voltage with base shorted to emitter; enables high-voltage transient tolerance
I_C	2.5 A continuous - Sustained collector current rating at T_C = 25 °C; sets baseline conduction capability
P_TOT	30 W - Total power dissipation at case temperature 25 °C; determines heatsink sizing requirement
R_thJC	4.16 °C/W - Junction-to-case thermal resistance; directly impacts thermal margin in surface-mount PCB layout
t_s	3.5 µs - Storage time under specified drive conditions; critical for minimum off-time and frequency scalability
E_AR	5 mJ - Repetitive avalanche energy (L = 2 mH, C = 1.8 nF); enables unclamped inductive switching reliability

Pinout & Package

DPAK (TO-252) type C package with exposed drain-connected tab (pin 2), standard 3-pin configuration optimized for surface-mount thermal performance and high-voltage isolation.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitter terminal	Low-side return path; connects to ground or current-sense resistor in common-emitter switch topology
2 (Tab / Collector)	Collector terminal (exposed metal tab)	Primary high-voltage output node; electrically connected to collector; requires insulated mounting or direct heatsink contact
3 (Base)	Control input	Current-driven gate interface; requires 0.6 A peak base drive for full saturation at I_C = 2 A

Key Features

Feature	Design Value
Intrinsic avalanche ruggedness	5 mJ repetitive energy rating without external clamping-reduces BOM count and layout complexity in ballast designs
High V_CES rating	1050 V collector-emitter withstand voltage-supports operation across wide input ranges and high dV/dt transients
Low V_CE(sat)	0.5 V typical at I_C = 2 A-minimizes conduction loss and improves efficiency in 20–100 kHz SMPS stages
Fast switching	t_s = 3.5 µs, t_f = 500 ns-enables higher-frequency operation while maintaining safe SOA margins
Thermal performance	R_thJC = 4.16 °C/W-allows effective heat transfer to PCB copper or heatsink, supporting compact power stage integration

Applications

Electronic Ballast Control

AC-DC Flyback Converter

Use Scenario: Driving resonant LC tank in 20–60 kHz fluorescent lamp ballasts with variable line input (100–277 VAC).

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling primary current; operates in hard-switched or quasi-resonant mode.

Use Value: Intrinsic 450 V sustaining voltage and 5 mJ avalanche energy eliminate need for Transil diodes, reducing component count and cost.

Use Scenario: Primary-side switch in universal-input offline flyback converters delivering up to 40 W.

IC Role / Device Role / Timing Role: Main power switch handling 400 V DC link; switched at 65–100 kHz with current-mode control.

Use Value: V_CES = 1050 V withstand and R_thJC = 4.16 °C/W enable reliable operation without derating at full load and ambient up to 70 °C.

LED Driver Power Stage

Industrial DC-DC Boost Converter

Use Scenario: Constant-current boost driver for high-bay LED fixtures powered from 277 VAC rectified bus.

IC Role / Device Role / Timing Role: High-side switch in boost topology; handles 400 V output and 1.5 A average inductor current.

Use Value: Low V_CE(sat) = 0.5 V reduces conduction loss, improving system efficiency by ~1.2% at full load.

Use Scenario: Step-up converter in industrial PLC power supply converting 24 VDC to 48 VDC at 5 A output.

IC Role / Device Role / Timing Role: Primary switching element in non-isolated boost stage; operated at 100 kHz with synchronous rectification.

Use Value: Fast t_s/t_f and stable h_FE (25–50 @ I_C = 0.45 A) ensure predictable drive requirements and minimal dead-time sensitivity.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STN9360	V_CEO = 400 V, I_C = 3 A, R_thJC = 3.3 °C/W, no avalanche rating	Lacks repetitive avalanche energy spec; requires external clamping in inductive switching	Preferred where higher current and lower thermal resistance are prioritized over unclamped ruggedness
BU508A	V_CEO = 1500 V, I_C = 12 A, TO-220 package, slower switching (t_f > 1 µs)	Higher voltage/current but larger footprint and lower frequency capability	Suitable for lower-frequency, higher-power linear or quasi-resonant ballasts where PCB space is not constrained

Compared with STN9360 and BU508A, BULD741T4 uniquely balances 450 V sustaining voltage, 5 mJ avalanche capability, and DPAK thermal performance-making it optimal for compact, high-reliability electronic ballasts and mid-power SMPS where clamping-free operation is required.

Availability

BULD741T4 is available at Aetrix Electronics and suitable for electronic ballasts, AC-DC flyback converters, LED drivers, and industrial DC-DC boost converters requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for BULD741T4 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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

BULD741T4 belongs to ST's high-voltage bipolar power transistor product line, engineered specifically for rugged, high-frequency switching in lighting and offline power conversion where intrinsic avalanche capability and thermal efficiency are critical.

FAQ

Is BULD741T4 pin-compatible with BU2520DX?

No. BU2520DX uses TO-220FP package with different pin order (collector-base-emitter), while BULD741T4 is DPAK (TO-252) with emitter-base-collector (tab) arrangement. Mechanical and thermal interfaces are incompatible; PCB redesign is required for substitution.

What is the maximum recommended gate/base drive current for reliable switching?

The datasheet specifies IBM = 3 A peak base current (t_P < 5 ms). For continuous operation, IB ≤ 1.5 A is recommended. At I_C = 2 A, 0.6 A DC base current ensures full saturation; exceeding 0.8 A provides margin against h_FE variation across temperature and lot.

Can BULD741T4 be used in zero-voltage switching (ZVS) topologies?

Yes-its t_s = 3.5 µs and t_f = 500 ns support ZVS implementation in resonant converters. However, its bipolar structure lacks body diode recovery characteristics of MOSFETs; snubber design must account for minority-carrier tail current during turn-off.

Does the exposed tab require electrical isolation from the heatsink?

Yes-the tab is internally connected to the collector. When mounted to a heatsink, an electrically insulating thermal pad or mica washer must be used unless the heatsink is fully isolated from system ground and other potentials. Clearance must meet creepage requirements for 1050 V transient ratings.

BULD741T4 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 2.5 A

Voltage - Collector Emitter Breakdown (Max):: 400 V

Vce Saturation (Max) @ Ib, Ic:: 1.5V @ 600mA, 2A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 450mA, 3V

Power - Max:: 30 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

BULD741T4 FAQ

1.How can I place an order for BULD741T4 through Aetrix?

Please submit a Request for Quotation (RFQ) for BULD741T4 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 BULD741T4 reliable?

The price and inventory of BULD741T4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BULD741T4 is usually 5 days.

3.What payment methods are accepted for BULD741T4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BULD741T4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BULD741T4?

BULD741T4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BULD741T4 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 BULD741T4?

For technical support, including BULD741T4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BULD741T4 requirements.

6.How does Aetrix verify that BULD741T4 is sourced from the original manufacturer or authorized distributors?

All BULD741T4 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 BULD741T4 meets industry standards.

7.What is the process for return or replacement of BULD741T4?

All BULD741T4 units undergo pre-shipment inspection (PSI). If there is an issue with BULD741T4, 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 BULD741T4 part is unused and in its original packaging.

Return procedure for BULD741T4:

1.Submit a request within 90 days.

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

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