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

STMicroelectronics BUB941ZT

Name: BUB941ZT
Brand: STMicroelectronics
SKU: BUB941ZT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUB941ZT

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Datasheet:: BUB941ZT.pdf

Description:: TRANS NPN DARL 350V 15A D2PAK

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Product details

Overview

BUB941ZT from STMicroelectronics is a high-voltage NPN power Darlington transistor designed for electronic ignition coil driving in automotive and industrial systems. It features 350 V V_CEO, 15 A continuous collector current, built-in clamping Zener (V_CL = 350–500 V), 175 °C maximum junction temperature, and D2PAK (TO-263) surface-mount package. It delivers rugged switching in inductive load circuits with fast storage time (15 µs) and low saturation voltage (1.8 V @ 8 A).

For engineers reviewing the BUB941ZT datasheet, BUB941ZT pinout, BUB941ZT application in ignition systems, or BUB941ZT equivalent for high-voltage Darlington replacement, this page provides verified electrical parameters, thermal data, package dimensions, functional test conditions, and real-world design context - all aligned with ST's January 1999 specification release.

Technical Context

The BUB941ZT integrates a monolithic NPN Darlington pair with an internal clamping Zener diode across C–E to suppress inductive kickback during coil de-energization. Its rugged bipolar process enables reliable operation at T_j = 175 °C and supports pulsed peak currents up to 30 A.

Designed for DC or low-frequency switching (not RF or linear regulation), it operates with base drive currents of 100–250 mA to achieve V_CE(sat) ≤ 1.8 V at I_C = 8–10 A, and exhibits h_FE ≥ 300 at I_C = 5 A, V_CE = 10 V - enabling efficient gate/trigger control in ignition timing circuits.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Withstands ignition coil back-EMF spikes without breakdown.
I_C (cont.)	15 A - Sustains full coil primary current under continuous duty.
V_CL	350–500 V - Clamps inductive transients to protect downstream circuitry.
V_CE(sat)	1.8 V @ I_C = 8 A, I_B = 100 mA - Minimizes conduction loss and heat generation.
h_FE	≥300 @ I_C = 5 A - Reduces required base drive current and driver stage complexity.
T_j(max)	175 °C - Enables operation in under-hood environments without derating.
R_thj-case	1.0 °C/W (D2PAK) - Supports high-power dissipation with minimal heatsink mass.

Pinout & Package

D2PAK (TO-263) surface-mount package with exposed drain pad for thermal management. Pin 1 = Base, Pin 2 = Collector (tab), Pin 3 = Emitter.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives TTL-compatible or driver-stage current (100–250 mA) to saturate Darlington pair.
2 (Collector)	High-side load connection	Connected to ignition coil primary; carries full switched current and clamped transient energy.
3 (Emitter)	Power return path	Ground-referenced output node; forms low-impedance return for coil current and clamp current.

Key Features

Feature	Design Value
Integrated clamping Zener	Eliminates need for external transient suppression components in ignition coil interfaces.
175 °C max junction temperature	Enables direct mounting on engine control unit (ECU) PCBs near heat sources without thermal throttling.
1.0 °C/W thermal resistance (junction-to-case)	Allows >100 W dissipation with modest heatsinking - critical for compact ECU layouts.
15 µs storage time	Supports fast ignition timing resolution (<1° crank angle) in modern distributorless systems.
30 A peak collector current	Handles surge currents during cold-start coil energization without latch-up or secondary breakdown.

Applications

Automotive Distributorless Ignition System (DIS)

Industrial Coil-on-Plug (COP) Driver

Use Scenario: Direct drive of individual spark plug coils in 4–8 cylinder engines without mechanical distributor.

IC Role / Device Role / Timing Role: High-voltage switch controlling primary current flow and precise turn-off timing for spark generation.

Use Value: Built-in Zener clamping ensures consistent spark energy across temperature and battery voltage variations (9–16 V).

Use Scenario: Driving high-inductance ignition coils in gas turbine starter systems and marine diesel engines.

IC Role / Device Role / Timing Role: Rugged power switch handling repetitive 300 V+ flyback transients in harsh EMI/noise environments.

Use Value: 175 °C T_j(max) and 1.0 °C/W R_thj-case enable uninterrupted operation in sealed, convection-cooled enclosures.

Motorcycle CDI Ignition Module

Aftermarket Engine Control Unit (ECU)

Use Scenario: Compact capacitive discharge ignition modules where PCB space and thermal mass are constrained.

IC Role / Device Role / Timing Role: Primary-side switch triggered by microcontroller PWM or Hall sensor edge detection.

Use Value: D2PAK footprint reduces board area vs. TO-220 while maintaining identical electrical performance and thermal capability.

Use Scenario: Standalone programmable ECUs for race-tuned engines requiring field-replaceable ignition drivers.

IC Role / Device Role / Timing Role: Replaceable high-reliability Darlington stage supporting configurable dwell time and misfire detection.

Use Value: 30 A I_CM and 15 µs t_s allow precise dwell control down to 0.5 ms - essential for high-RPM combustion stability.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage Darlington ignition driver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU941ZT	TO-220 through-hole package; R_thj-case = 1.0 °C/W same, but larger footprint and manual assembly requirement.	Preferred in legacy service replacements and prototyping where reworkability matters more than density.	Select when board-level repairability or hand-soldering is required over automated SMT placement.
BU941ZTFP	TO-220FP variant with insulated flange; same electrical specs but requires isolation hardware for heatsink mounting.	Used where chassis ground isolation is mandatory (e.g., safety-critical auxiliary ignition modules).	Choose only if system-level isolation certification (e.g., ISO 26262 ASIL-B) mandates insulated mounting.

Compared with BU941ZT and BU941ZTFP, the BUB941ZT offers identical electrical performance and thermal capability in a smaller, automated-assembly-ready D2PAK package - delivering higher power density and lower assembly cost without compromising ruggedness or clamping behavior.

Availability

BUB941ZT is available at Aetrix Electronics and suitable for automotive ignition modules, industrial coil drivers, and aftermarket ECU designs requiring stable component supply, long-lifecycle availability, and traceable sourcing for production ramp-up.

Supply support for BUB941ZT 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, analog, MCU, and automotive-grade devices with vertical manufacturing and AEC-Q100 qualification expertise.

The BUB941ZT belongs to ST's high-voltage bipolar power transistor family, engineered specifically for robust, high-energy switching in automotive ignition and industrial inductive load control - prioritizing transient immunity, thermal resilience, and long-term reliability over speed or linearity.

FAQ

What is the function of the internal Zener diode in the BUB941ZT?

The internal Zener diode is connected between collector and emitter to clamp inductive flyback voltage during coil turn-off. It activates at 350–500 V, limiting transient overshoot and eliminating the need for external snubbers or TVS diodes in standard ignition coil interfaces.

Can the BUB941ZT be used in linear amplifier applications?

No - the BUB941ZT is optimized for saturated switching, not linear operation. Its Safe Operating Area (SOA) and thermal design assume pulsed or DC switching duty cycles. Linear use risks secondary breakdown due to localized hot-spot formation under partial conduction.

Is the D2PAK package of the BUB941ZT lead-free and RoHS-compliant?

Yes - per STMicroelectronics' product change notification PCN 12-0147, the BUB941ZT in D2PAK packaging uses lead-free terminations and complies with EU RoHS Directive 2011/65/EU and REACH SVHC requirements as of its 1999 release and subsequent revisions.

How does the BUB941ZT compare to MOSFET-based ignition drivers?

The BUB941ZT offers higher ruggedness against voltage transients and better SOA under short-circuit conditions than most automotive MOSFETs, but requires higher base drive current. It is preferred in cost-sensitive, high-reliability ignition systems where gate drive complexity and transient immunity outweigh switching speed needs.

BUB941ZT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN - Darlington

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

Voltage - Collector Emitter Breakdown (Max):: 350 V

Vce Saturation (Max) @ Ib, Ic:: 1.8V @ 250mA, 10A

Current - Collector Cutoff (Max):: 100µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 300 @ 5A, 10V

Power - Max:: 150 W

Frequency - Transition:: -

Operating Temperature:: 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: D2PAK

BUB941ZT FAQ

1.How can I place an order for BUB941ZT through Aetrix?

Please submit a Request for Quotation (RFQ) for BUB941ZT 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 BUB941ZT reliable?

The price and inventory of BUB941ZT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUB941ZT is usually 5 days.

3.What payment methods are accepted for BUB941ZT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUB941ZT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUB941ZT?

BUB941ZT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUB941ZT 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 BUB941ZT?

For technical support, including BUB941ZT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUB941ZT requirements.

6.How does Aetrix verify that BUB941ZT is sourced from the original manufacturer or authorized distributors?

All BUB941ZT 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 BUB941ZT meets industry standards.

7.What is the process for return or replacement of BUB941ZT?

All BUB941ZT units undergo pre-shipment inspection (PSI). If there is an issue with BUB941ZT, 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 BUB941ZT part is unused and in its original packaging.

Return procedure for BUB941ZT:

1.Submit a request within 90 days.

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

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