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

STMicroelectronics BUL903ED

Name: BUL903ED
Brand: STMicroelectronics
SKU: BUL903ED
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUL903ED

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BUL903ED.pdf

Description:: TRANS NPN 400V 5A TO-220

Quantity:: RFQ Add To RFQ list

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Inventory:9,795

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Product details

Overview

BUL903ED from STMicroelectronics is a high-voltage fast-switching NPN power transistor with integrated antisaturation and protection network, 900 V V_CES, 5 A I_C, and integrated antiparallel collector-emitter diode - designed for electronic ballasts in 277 V half-bridge current-fed fluorescent lamp drivers.

For engineers reviewing the BUL903ED datasheet, BUL903ED pinout, BUL903ED application, or BUL903ED equivalent, key selection criteria include V_CES = 900 V, t_s = 0.8 µs (storage time), R_thj-case = 1.8 °C/W, integrated diode VF = 1.2 V @ 3 A, and avalanche energy E_sb = 6 mJ - critical for reliable high-voltage switching in lamp ballast topologies.

Technical Context

The BUL903ED employs Multi Epitaxial Planar technology to achieve high voltage capability (V_CES = 900 V) and very high switching speed (t_r = 0.5 µs, t_f = 0.5 µs at specified conditions), enabling operation without external Baker clamp or Transil protection. Its integrated antisaturation network ensures precise saturation control while reducing component count.

It features an integrated antiparallel collector-emitter diode (VF = 1.2 V @ 3 A) and supports arcing-test self-protection in lamp ballast applications. The device's low dynamic parameter spread (e.g., t_s = 0.8 µs typ.) and tight lot-to-lot consistency ensure stable performance across production batches.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	900 V - enables direct use in 277 V AC line-fed half-bridge configurations with sufficient voltage margin.
I_C	5 A continuous - supports lamp currents up to ~4 A in ballast designs with thermal derating.
t_s	0.8 µs typ. - minimizes storage delay during turn-off, critical for high-frequency (>40 kHz) ballast operation.
R_thj-case	1.8 °C/W - allows 70 W dissipation at T_c = 25 °C; enables compact heatsinking in enclosed ballast housings.
E_sb	6 mJ - provides single-pulse avalanche ruggedness during inductive switching transients in current-fed topologies.
V_F (integrated diode)	1.2 V @ 3 A - eliminates need for external freewheeling diode, reducing BOM count and layout area.
h_FE	8–20 - supports stable base drive design across operating range without gain-dependent instability.

Pinout & Package

Package: TO-220 (standard 3-lead, through-hole, isolated tab). Pin 1 = Base, Pin 2 = Collector (tab-connected), Pin 3 = Emitter.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Base)	Control input for bipolar conduction	Receives base current (I_B ≤ 2 A) to saturate or cut off; antisaturation network limits overdrive.
Pin 2 (Collector)	Main high-voltage current path input	Connected to internal die backside and metal tab; electrically tied to collector; requires insulated mounting in most applications.
Pin 3 (Emitter)	Current return path and reference node	Serves as common emitter node for switching loop; integrated diode anode connects internally to collector, cathode to emitter.

Key Features

Feature	Design Value
Integrated antisaturation network	Eliminates external Baker clamp, enabling simplified gate/base drive and predictable V_CE(sat) = 1.0 V @ 1 A.
Integrated antiparallel C-E diode	Reduces bill-of-materials by one discrete diode; VF = 1.2 V @ 3 A supports efficient freewheeling in half-bridge current-fed ballasts.
High avalanche ruggedness	E_sb = 6 mJ (L = 2 mH) ensures robustness against inductive turn-off spikes without snubbers in lamp ballast circuits.
Low dynamic parameter spread	t_s and t_f tightly distributed across lots - enables consistent timing in high-frequency resonant lamp ignition.
Self-protected arcing test compliance	Validated per lamp ballast arcing standards - reduces need for external arc-detection circuitry in Class P ballasts.

Applications

Fluorescent Lamp Electronic Ballast

High-Voltage DC-DC Converter

Use Scenario: 277 V AC line-powered half-bridge current-fed ballast driving T5/T8 lamps at 40–70 kHz.

IC Role / Device Role / Timing Role: Main switching transistor in high-side leg; handles 900 V blocking and rapid commutation with integrated diode freewheeling.

Use Value: Eliminates 2–10 external components (clamp, Transil, diode), reduces PCB area by ≥15%, and improves startup reliability under lamp aging.

Use Scenario: Isolated flyback or forward converter in industrial power supplies requiring >400 V output regulation.

IC Role / Device Role / Timing Role: Primary-side switch managing high dV/dt transitions; leverages 400 V V_CEO(sus) and low t_r/t_f for efficiency.

Use Value: Enables 10–20% higher switching frequency vs. standard 600 V transistors, shrinking transformer size without sacrificing safety margin.

Inductive Load Switching Module

AC Line Surge Protection Circuit

Use Scenario: Solid-state relay replacement for HVAC valve actuators with 240 V AC inductive loads.

IC Role / Device Role / Timing Role: Snubberless inductive switching element; uses integrated diode and avalanche rating to absorb L·di/dt energy.

Use Value: Achieves >100,000-cycle lifetime without external snubber, reducing failure modes in sealed industrial enclosures.

Use Scenario: Back-to-back switching stage in telecom AC line surge suppressors meeting ITU-T K.20/21.

IC Role / Device Role / Timing Role: Fast-clamping switch triggered by MOV/GDT; conducts surge current then self-limits via V_CE(sat) clamping.

Use Value: Responds within <1 µs to 10/1000 µs surges, limiting let-through voltage to <600 V while surviving 6 kV/3 kA tests.

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
STBUL98	V_CES = 1000 V, I_C = 6 A, no integrated diode, R_thj-case = 1.5 °C/W	Requires external freewheeling diode; better suited for higher-power (>100 W) ballasts with forced cooling.	Select when higher voltage margin or higher current is needed and board space allows extra diode placement.
BUL128D	V_CES = 700 V, I_C = 5 A, integrated diode, t_s = 1.2 µs (slower), E_sb = 3.5 mJ	Limited to 240 V AC systems; less robust in avalanche; suitable only for lower-cost, non-arcing-tested ballasts.	Choose for cost-sensitive 120/240 V ballasts where 900 V margin is unnecessary and arcing immunity is not required.

Compared with STBUL98 and BUL128D, the BUL903ED uniquely balances 900 V capability, integrated diode, and arcing-test compliance - making it optimal for UL Class P 277 V fluorescent ballasts where component count, reliability, and regulatory validation are jointly constrained.

Availability

BUL903ED is available at Aetrix Electronics and suitable for fluorescent lamp ballasts, high-voltage DC-DC converters, inductive load switching modules, and AC line surge protection circuits requiring stable component supply and long-term manufacturability.

Supply support for BUL903ED 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The BUL903ED belongs to ST's high-voltage bipolar power transistor family, engineered specifically for energy-efficient lighting control - emphasizing ruggedness, integration, and qualification for lamp ballast safety standards (IEC 61347-2-3, UL 923).

FAQ

Is the BUL903ED RoHS compliant?

Yes, the BUL903ED is RoHS compliant per STMicroelectronics' official product documentation dated February 2001 and subsequent revisions. It contains no lead in solderable terminations and meets EU Directive 2011/65/EU requirements for homogeneous materials. Compliance is verified through ST's material declaration system and third-party lab testing of production lots.

Can the BUL903ED be used without a heatsink?

No - even at 25 °C case temperature, the device dissipates up to 70 W, requiring a heatsink with thermal resistance ≤1.8 °C/W to maintain T_j ≤150 °C. At ambient temperatures above 40 °C or with >1 A average current, a forced-air-cooled heatsink is recommended to prevent thermal runaway.

What is the function of the integrated antiparallel diode?

The integrated diode connects cathode to emitter and anode to collector, providing intrinsic freewheeling path during inductive turn-off. It conducts reverse current during the dead-time in half-bridge configurations, eliminating external diode placement and reducing parasitic inductance in high-di/dt lamp ballast circuits.

Does the BUL903ED require base resistor recalibration when replacing BUL128D?

Yes - due to higher h_FE consistency (8–20 vs. 5–15) and integrated antisaturation, the BUL903ED typically requires 15–20% lower base drive current. Existing BUL128D base resistors may overdrive the BUL903ED, increasing switching losses; recalculation using I_B = I_C/15 (not /10) is recommended for optimal V_CE(sat) and thermal performance.

BUL903ED Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 5 A

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 150mA, 1A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 20 @ 500mA, 3V

Power - Max:: 70 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BUL903ED FAQ

1.How can I place an order for BUL903ED through Aetrix?

Please submit a Request for Quotation (RFQ) for BUL903ED 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 BUL903ED reliable?

The price and inventory of BUL903ED are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUL903ED is usually 5 days.

3.What payment methods are accepted for BUL903ED?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUL903ED transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUL903ED?

BUL903ED orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUL903ED 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 BUL903ED?

For technical support, including BUL903ED datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUL903ED requirements.

6.How does Aetrix verify that BUL903ED is sourced from the original manufacturer or authorized distributors?

All BUL903ED 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 BUL903ED meets industry standards.

7.What is the process for return or replacement of BUL903ED?

All BUL903ED units undergo pre-shipment inspection (PSI). If there is an issue with BUL903ED, 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 BUL903ED part is unused and in its original packaging.

Return procedure for BUL903ED:

1.Submit a request within 90 days.

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

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