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

STMicroelectronics BU941ZTFP

Name: BU941ZTFP
Brand: STMicroelectronics
SKU: BU941ZTFP
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BU941ZTFP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3 Full Pack

Datasheet:: BU941ZTFP.pdf

Description:: TRANS NPN DARL 350V 15A TO-220AB

Quantity:: RFQ Add To RFQ list

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Inventory:6,404

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Product details

Overview

BU941ZTFP from STMicroelectronics is a high-voltage NPN power Darlington transistor designed for electronic ignition coil driving, featuring built-in clamping Zener (V_CL = 350–500 V), 350 V V_CEO, 15 A continuous collector current, and 175 °C maximum junction temperature in D2PAK (TO-263) surface-mount package.

For engineers reviewing the BU941ZTFP datasheet, BU941ZTFP pinout, BU941ZTFP application, or BU941ZTFP equivalent, key selection criteria include clamped inductive switching capability, rugged thermal performance under pulsed ignition loads, and compatibility with 7 mH ignition coils at 12–24 V supply rails.

Technical Context

This Darlington device integrates a monolithic clamping Zener diode across C–E to suppress inductive kickback during coil de-energization, eliminating external snubbers in automotive ignition systems. Its high h_FE (min 300 at I_C = 5 A) enables direct drive from low-current microcontroller outputs via base resistor networks.

Rated for DC and pulsed operation (300 µs pulse, 1.5% duty cycle), it delivers 15 A continuous collector current with 1.8 V V_CE(sat) at I_C = 8 A / I_B = 100 mA and supports fast switching with t_s = 15 µs and t_f = 0.5 µs into 7 mH inductive loads.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Withstands peak coil back-EMF without external clamp
I_C (continuous)	15 A - Sustains full primary coil current in 12 V/24 V ignition systems
V_CL	350–500 V - Integrated Zener limits voltage during turn-off, protecting driver and MCU
V_CE(sat)	1.8 V @ I_C=8 A, I_B=100 mA - Low conduction loss reduces thermal stress in compact layouts
h_FE	300 min @ I_C=5 A - Enables direct drive from 5 V logic with ~17 mA base current
T_j(max)	175 °C - Supports operation in engine bay environments without derating below 150 °C ambient
R_thj-case	2.7 °C/W - Enables 55 W dissipation at T_c = 25 °C in D2PAK package

Pinout & Package

D2PAK (TO-263) surface-mount package with exposed drain pad (pin 2) for thermal and electrical connection to PCB ground plane. Three-terminal configuration optimized for high-current switching with minimal parasitic inductance.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives base current to saturate Darlington pair; requires series resistor for current limiting
2 (Collector)	High-side switch output	Connected to ignition coil primary; carries full load current and clamped flyback energy
3 (Emitter)	Power return	Common emitter node tied to system ground; forms low-impedance path for coil current return

Key Features

Feature	Design Value
Integrated clamping Zener	Eliminates need for external TVS or RCD snubber in ignition coil drivers
High ruggedness rating	Withstands repetitive 300 µs pulses at 30 A peak without degradation
Wide operating temperature range	Functional from –65 °C to +175 °C junction, suitable for under-hood deployment
Low saturation voltage	1.8 V V_CE(sat) minimizes power loss and heatsink requirements in space-constrained modules

Applications

Automotive Ignition Systems

Industrial Ignition Modules

Use Scenario: Driving primary winding of distributorless ignition coils in gasoline engines.

IC Role / Device Role / Timing Role: High-current, high-voltage switch controlling coil energization/de-energization timing.

Use Value: Built-in clamping ensures reliable spark generation without external protection components.

Use Scenario: Solid-state replacement for mechanical contact points in industrial burners and furnaces.

IC Role / Device Role / Timing Role: Primary-side power switch triggered by PLC or timer circuits.

Use Value: 175 °C T_j(max) and rugged SOA support continuous operation in hot enclosures.

Motorcycle CDI Units

Aftermarket Ignition Controllers

Use Scenario: Compact capacitive discharge ignition (CDI) modules for two-wheeled vehicles.

IC Role / Device Role / Timing Role: Fast-switching Darlington stage discharging capacitor bank into coil primary.

Use Value: 15 µs storage time enables precise spark timing control at high RPM.

Use Scenario: Programmable ignition timing controllers used in racing or retrofit applications.

IC Role / Device Role / Timing Role: Final output stage interfacing microcontroller PWM signals to ignition coil.

Use Value: High h_FE allows direct drive from 3.3 V/5 V MCU GPIO with minimal external components.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STGD10NB60KD	600 V, 10 A N-channel MOSFET with integrated gate driver; no internal clamp diode	Requires external Zener clamp; faster switching but higher gate drive complexity	Preferred for high-frequency (>10 kHz) digital ignition where lower switching loss outweighs added component count
BU941ZT	Identical die and specs; TO-220 through-hole package instead of D2PAK	Manual assembly or legacy board designs requiring leaded mounting	Select when thermal interface constraints favor TO-220 heatsinking or production uses wave soldering

Compared with BU941ZTFP, STGD10NB60KD offers superior switching speed but demands external clamping and gate drive design effort, while BU941ZT provides identical electrical performance in a through-hole form factor better suited for prototyping or repair scenarios.

Availability

BU941ZTFP is available at Aetrix Electronics and suitable for automotive ignition systems, industrial burner controls, motorcycle CDI units, and aftermarket ignition controllers requiring stable component supply across extended temperature and high-reliability environments.

Supply support for BU941ZTFP 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 management, automotive ICs, and discrete devices with broad industrial and automotive qualification.

The BU941ZT family belongs to ST's high-voltage bipolar power transistor product line, engineered specifically for robust, high-energy inductive switching in engine management and industrial ignition applications.

FAQ

What is the purpose of the built-in Zener diode in BU941ZTFP?

The integrated Zener diode clamps collector-emitter voltage during inductive turn-off, limiting V_CE to 350–500 V. This protects the transistor and upstream circuitry from destructive flyback spikes generated by ignition coils, eliminating the need for external snubber networks in most designs.

Can BU941ZTFP be used with 24 V battery systems?

Yes - BU941ZTFP is rated for V_CEO = 350 V and operates reliably with 24 V nominal supplies. Its 175 °C max junction temperature and 55 W power dissipation in D2PAK enable sustained use in 24 V commercial vehicle ignition systems, provided thermal design maintains case temperature ≤ 25 °C.

How does BU941ZTFP differ from BU941ZT?

BU941ZTFP and BU941ZT share identical silicon die, electrical specifications, and thermal ratings. The only difference is packaging: BU941ZTFP uses surface-mount D2PAK (TO-263), while BU941ZT uses through-hole TO-220. Pinout and footprint are not interchangeable.

Is a base resistor required when driving BU941ZTFP from a microcontroller?

Yes - a series base resistor is mandatory to limit base current. For example, with a 5 V MCU output and V_BE(sat) ≈ 2.5 V, a 220 Ω resistor delivers ~11.4 mA base current, sufficient to saturate the Darlington at I_C = 10 A (h_FE ≥ 300). Undriven base risks thermal runaway.

BU941ZTFP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3 Full Pack

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:: 55 W

Frequency - Transition:: -

Operating Temperature:: 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220AB

BU941ZTFP FAQ

1.How can I place an order for BU941ZTFP through Aetrix?

Please submit a Request for Quotation (RFQ) for BU941ZTFP 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 BU941ZTFP reliable?

The price and inventory of BU941ZTFP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU941ZTFP is usually 5 days.

3.What payment methods are accepted for BU941ZTFP?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU941ZTFP transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BU941ZTFP?

BU941ZTFP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BU941ZTFP 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 BU941ZTFP?

For technical support, including BU941ZTFP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU941ZTFP requirements.

6.How does Aetrix verify that BU941ZTFP is sourced from the original manufacturer or authorized distributors?

All BU941ZTFP 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 BU941ZTFP meets industry standards.

7.What is the process for return or replacement of BU941ZTFP?

All BU941ZTFP units undergo pre-shipment inspection (PSI). If there is an issue with BU941ZTFP, 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 BU941ZTFP part is unused and in its original packaging.

Return procedure for BU941ZTFP:

1.Submit a request within 90 days.

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

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