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

STMicroelectronics BUXD87T4

Name: BUXD87T4
Brand: STMicroelectronics
SKU: BUXD87T4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUXD87T4

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BUXD87T4.pdf

Description:: TRANS NPN 450V 0.5A DPAK

Quantity:: RFQ Add To RFQ list

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Inventory:9,235

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Product details

Overview

BUXD87T4 from STMicroelectronics is a high-voltage NPN power transistor in surface-mount DPAK (TO-252) package, rated for 450 V V_CEO, 0.5 A continuous collector current, and 20 W total dissipation at T_c = 25 °C; used as main switch in offline SMPS with flyback or forward topologies.

For engineers reviewing the BUXD87T4 datasheet, BUXD87T4 pinout, BUXD87T4 application, or BUXD87T4 equivalent, key selection criteria include V_CEO derating at elevated T_j, h_FE stability across I_C = 40–50 mA, safe operating area under resistive switching, and thermal resistance R_thj-case = 6.25 °C/W.

Technical Context

The BUXD87T4 employs High Voltage Multi Epitaxial Planar technology to achieve robust avalanche ruggedness and fast switching performance, with t_s = 4.5 µs and t_f = 0.5 µs under specified resistive load conditions (V_CC = 250 V, I_C = 200 mA).

It features reverse-biased SOA compliance up to 450 V, V_CE(sat) ≤ 1.0 V at I_C = 0.2 A / I_B = 0.02 A, and guaranteed h_FE ≥ 12 at I_C = 50 mA / V_CE = 5 V - enabling stable base drive design in fixed-frequency PWM controllers.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	450 V - maximum DC collector-emitter voltage before breakdown under open-base condition; defines primary isolation rating in offline AC/DC inputs.
I_C	0.5 A - continuous collector current limit at T_c = 25 °C; sets max output power capability in <100 W SMPS designs.
P_tot	20 W - total power dissipation at case temperature 25 °C; requires heatsink for sustained operation above ~5 W.
h_FE	12–50 - DC current gain range at I_C = 40–50 mA / V_CE = 5 V; enables predictable base resistor sizing for saturation control.
R_thj-case	6.25 °C/W - junction-to-case thermal resistance; determines temperature rise per watt dissipated when mounted on copper pad.
t_s/t_f	4.5 µs / 0.5 µs - storage and fall time under V_CC = 250 V, I_C = 200 mA; constrains minimum achievable switching frequency in hard-switched topologies.

Pinout & Package

Package: Surface-mount DPAK (TO-252), 3-terminal, single-die NPN transistor with exposed drain-connected tab (pin 2) for thermal and electrical connection.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitter terminal	Low-side reference node; connects to ground or source return path in buck/flyback configurations.
2 (Collector / Tab)	Collector terminal & thermal pad	High-voltage output node; electrically and thermally connected to PCB copper pour for heat transfer and EMI reduction.
3 (Base)	Control input	Current-driven gate; requires external series resistor to limit I_B ≤ 0.3 A peak and ensure saturation at target I_C.

Key Features

Feature	Design Value
High-voltage blocking	Rated V_CEO = 450 V supports direct rectified 230 VAC mains operation without cascading devices.
Fast switching	t_s + t_f = 5 µs enables operation up to ~100 kHz in non-resonant converters with low switching loss.
High h_FE	Min. h_FE = 12 at I_C = 50 mA reduces base drive power requirement vs. low-gain alternatives.
Avalanche ruggedness	Guaranteed reverse-biased SOA up to 450 V ensures reliability during inductive turn-off transients.

Applications

Offline Flyback SMPS

AC-DC Adapter Primary Switch

Use Scenario: 36 W universal-input (85–265 VAC) flyback converter powering USB-C PD accessories.

IC Role / Device Role / Timing Role: Main power switch controlled by UC3842-derived PWM IC; operates at 65 kHz with discontinuous conduction mode.

Use Value: V_CEO margin > 2× peak line-referred voltage ensures long-term reliability under surge conditions.

Use Scenario: Compact wall-mounted 12 V/2 A adapter for IoT sensors with no fan cooling.

IC Role / Device Role / Timing Role: Single-ended primary switch in self-oscillating quasi-resonant topology; driven by internal oscillator.

Use Value: R_thj-case = 6.25 °C/W allows 12 cm² 2-oz copper pad to maintain T_j < 125 °C at full load.

Industrial Control Power Supply

LED Driver Primary Switch

Use Scenario: 24 V/1 A auxiliary supply in PLC backplane with wide ambient range (−40 to +70 °C).

IC Role / Device Role / Timing Role: Hard-switched forward converter primary switch; synchronized to system clock for EMI control.

Use Value: h_FE ≥ 12 at −40 °C ensures sufficient base current for saturation without overdesigning driver stage.

Use Scenario: 48 V/0.7 A constant-current LED driver for street lighting with TRIAC dimming compatibility.

IC Role / Device Role / Timing Role: Leading-edge dimmable primary switch handling phase-cut waveforms with high dv/dt stress.

Use Value: Reverse-biased SOA compliance prevents failure during zero-crossing commutation spikes up to 600 Vpk.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STN9260	V_CEO = 600 V, I_C = 1.5 A, P_tot = 30 W, TO-220 package	Higher voltage headroom and current capacity; requires through-hole mounting and larger heatsink	Select when >450 V line surges or >0.5 A peak load demand exist; not drop-in due to package and pinout mismatch
MJD122T4	V_CEO = 100 V, I_C = 3 A, P_tot = 20 W, DPAK package	Lower voltage rating but higher current; unsuitable for direct rectified AC mains	Only viable in low-line (<120 VAC) or DC-fed isolated converters; requires redesign of snubber and transformer turns ratio

Compared with STN9260 and MJD122T4, BUXD87T4 uniquely balances 450 V blocking, DPAK mountability, and proven SOA in cost-sensitive offline SMPS - making it optimal where board space, thermal management, and mains-rated safety co-constrain the design.

Availability

BUXD87T4 is available at Aetrix Electronics and suitable for offline flyback SMPS, AC-DC adapters, industrial control power supplies, and LED driver primary switching requiring stable component supply and long-lifecycle support.

Supply support for BUXD87T4 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 industrial, automotive, and consumer markets.

The BUXD87 series belongs to ST's high-voltage bipolar power transistor product line, engineered specifically for reliable, cost-effective primary-side switching in non-isolated and isolated AC/DC converters up to 100 W.

FAQ

What is the maximum allowable junction temperature for BUXD87T4?

The absolute maximum operating junction temperature is 150 °C, as specified in the Absolute Maximum Ratings table. Operation above this limit risks permanent degradation of h_FE and increased leakage current; thermal design must ensure T_j remains below 150 °C under worst-case ambient and power dissipation conditions.

Can BUXD87T4 be used in avalanche mode?

Yes - the device is characterized for reverse-biased safe operating area (SOA) up to 450 V, confirming controlled avalanche capability during inductive turn-off. However, repetitive avalanche operation requires strict energy limiting via snubber networks and must stay within the published SOA curve boundaries shown in the datasheet.

Is the collector tab electrically isolated in the DPAK package?

No - in the BUXD87T4 DPAK (TO-252) package, the collector is internally bonded to the exposed metal tab. This tab must be electrically connected to the collector net on the PCB and thermally coupled to a copper pour; isolation requires insulating thermal interface material and careful layout to avoid shorting.

What base drive current is required to saturate BUXD87T4 at I_C = 0.4 A?

With minimum h_FE = 12 at I_C = 50 mA and typical h_FE ≈ 30–40 at I_C = 0.4 A, a base current of ≥15 mA ensures saturation. Using the datasheet's V_BE(sat) = 1 V at I_C = 0.2 A / I_B = 0.02 A, a 470 Ω base resistor from a 5 V driver yields ~8.5 mA - insufficient; 220 Ω is recommended for margin.

BUXD87T4 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):: 500 mA

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 20mA, 200mA

Current - Collector Cutoff (Max):: -

DC Current Gain (hFE) (Min) @ Ic, Vce:: 12 @ 40mA, 5V

Power - Max:: 20 W

Frequency - Transition:: 20MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

BUXD87T4 FAQ

1.How can I place an order for BUXD87T4 through Aetrix?

Please submit a Request for Quotation (RFQ) for BUXD87T4 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 BUXD87T4 reliable?

The price and inventory of BUXD87T4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUXD87T4 is usually 5 days.

3.What payment methods are accepted for BUXD87T4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUXD87T4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUXD87T4?

BUXD87T4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUXD87T4 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 BUXD87T4?

For technical support, including BUXD87T4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUXD87T4 requirements.

6.How does Aetrix verify that BUXD87T4 is sourced from the original manufacturer or authorized distributors?

All BUXD87T4 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 BUXD87T4 meets industry standards.

7.What is the process for return or replacement of BUXD87T4?

All BUXD87T4 units undergo pre-shipment inspection (PSI). If there is an issue with BUXD87T4, 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 BUXD87T4 part is unused and in its original packaging.

Return procedure for BUXD87T4:

1.Submit a request within 90 days.

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

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