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

STMicroelectronics BU941ZP

Name: BU941ZP
Brand: STMicroelectronics
SKU: BU941ZP
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BU941ZP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-247-3

Datasheet:: BU941ZP.pdf

Description:: TRANS NPN DARL 350V 15A TO-247-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BU941ZP from STMicroelectronics is a high-voltage NPN power Darlington transistor designed for automotive electronic ignition coil driving, featuring 350 V V_CEO, 15 A continuous collector current, 180 W total dissipation (TO-3), built-in clamping zener, and U.L.-compliant fully insulated TO-3 package for direct heatsink mounting.

For engineers reviewing the BU941ZP datasheet, BU941ZP pinout, BU941ZP application in ignition systems, or BU941ZP equivalent for high-ruggedness inductive switching, this device delivers validated clamping voltage (350–500 V), low V_CE(sat) (1.8–2.0 V at 8–12 A), and 200 °C max junction temperature-critical for under-hood reliability.

Technical Context

This Darlington uses multiepitaxial planar bipolar technology with integrated zener clamping across C–E to suppress inductive kickback during coil de-energization. Its ruggedness stems from 200 °C T_j(max), 2500 V RMS insulation rating, and SOA-optimized layout for repetitive 30 A peak current pulses.

The device operates as a single-stage high-side switch in 12 V/24 V automotive ignition circuits, where base drive (≤1 A) controls full coil energy discharge. Switching performance is characterized by 15 µs storage time and 0.5 µs fall time into 7 mH inductive load with 300 V clamp reference.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Withstands ignition coil flyback transients without breakdown
I_C (continuous)	15 A - Sustains full primary coil current in 4–8 cylinder engines
V_CL	350–500 V - Clamps inductive spikes to protect downstream circuitry
V_CE(sat)	1.8–2.0 V @ 8–12 A - Minimizes conduction loss and thermal stress
R_thj-case	0.97 °C/W (TO-3) - Enables efficient heatsinking in compact engine bays
T_j(max)	200 °C - Supports operation in under-hood environments up to 150 °C ambient
Visol	2500 V RMS - Allows safe mounting to chassis/heatsink without isolation hardware

Pinout & Package

BU941ZP is supplied in a fully insulated TO-3 metal package compliant with U.L. standards, enabling direct bolt-on mounting to grounded heatsinks without insulating washers. The case serves as the collector terminal.

Pin/Terminal	Circuit Role	Design Meaning
Tab (Case)	Collector	Electrically active collector terminal; provides primary thermal path to heatsink
Pin 1	Base	Control input requiring ~100–300 mA drive for full saturation at 8–12 A I_C
Pin 2	Emiter	Emitter output tied to ground or low-side return; completes main power path

Key Features

Feature	Design Value
Integrated clamping zener	350–500 V dynamic clamp eliminates need for external TVS in ignition coil driver stage
U.L.-rated insulation	2500 V RMS isolation enables direct mounting to conductive chassis without arcing risk
High T_j rating	200 °C maximum junction temperature supports sustained operation in sealed engine compartments
Rugged SOA	Validated 30 A peak current handling with 15 µs storage time ensures reliable coil switching at 100+ Hz
Multiepitaxial planar process	Reduces secondary breakdown risk and improves long-term reliability under repetitive surge conditions

Applications

Automotive Ignition Systems

Industrial Ignition Modules

Use Scenario: Driving primary winding of distributorless ignition coils in gasoline engines (4–12 cylinders).

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

Use Value: Built-in 350–500 V clamping prevents MOSFET or controller IC damage from inductive flyback.

Use Scenario: Solid-state replacement for mechanical contact points in industrial gas burner ignition control.

IC Role / Device Role / Timing Role: Rugged power switch triggering spark generation in high-duty-cycle combustion systems.

Use Value: 200 °C T_j(max) and 0.97 °C/W thermal resistance enable continuous operation in enclosed furnace enclosures.

Motorcycle CDI Units

Aftermarket Engine Management

Use Scenario: Compact capacitor discharge ignition (CDI) modules for 2-stroke and 4-stroke motorcycles.

IC Role / Device Role / Timing Role: Primary-side power switch synchronizing spark timing with crank position signals.

Use Value: Fully insulated TO-3 package allows PCB-mountable design without creepage distance compromises.

Use Scenario: Standalone ignition drivers in custom ECU designs for race engines or vintage car retrofits.

IC Role / Device Role / Timing Role: High-ruggedness actuator interfacing microcontroller PWM outputs to ignition coils.

Use Value: Validated 30 A peak current and 15 µs storage time support aggressive dwell-time tuning up to 10 ms.

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
BU941Z	Same die, non-insulated TO-3 package; 180 W P_tot, 200 °C T_j, no U.L. insulation	Requires insulating kit for heatsink mounting; higher thermal performance but added BOM cost	Select when thermal margin >0.5 °C/W is critical and isolation hardware is acceptable
BU941ZPFI	Same insulated TO-3 package, but rated for 175 °C T_j and 155 W P_tot; identical pinout and clamping	Slightly lower power handling; optimized for cost-sensitive production with same mounting footprint	Select when operating ambient stays below 125 °C and 155 W dissipation suffices

Compared with BU941Z and BU941ZPFI, the BU941ZP uniquely balances full insulation, 200 °C junction rating, and 180 W dissipation-making it optimal for high-reliability, thermally constrained ignition applications where mounting simplicity and ruggedness are co-prioritized.

Availability

BU941ZP is available at Aetrix Electronics and suitable for automotive ignition systems, industrial burner controls, motorcycle CDI units, and aftermarket engine management requiring stable component supply and long-lifecycle availability.

Supply support for BU941ZP 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, and automotive-grade discrete and integrated solutions.

The BU941ZP belongs to ST's high-voltage bipolar power transistor product line, engineered specifically for robust, high-temperature switching in automotive ignition and industrial inductive load control.

FAQ

What is the maximum recommended base drive current for reliable saturation?

The BU941ZP achieves full saturation at I_C = 12 A with I_B = 300 mA, per datasheet test condition. For continuous operation, base current should not exceed 1 A (absolute max), and a 47 Ω base resistor with 12 V drive yields ~255 mA-within safe linear region and sufficient for 10 A loads.

Can BU941ZP be used without a heatsink in low-duty-cycle applications?

No. Even at 10% duty cycle, 10 A I_C with 1.8 V V_CE(sat) generates 18 W average power. With R_thj-case = 0.97 °C/W, junction temperature would exceed 200 °C without heatsinking. A minimum 0.5 °C/W heatsink is required for any sustained current >2 A.

Does the built-in zener require external biasing or series resistance?

No. The clamping zener is monolithically integrated between collector and emitter and activates automatically when V_CE exceeds ~350 V. No external components are needed-the device self-clamps during inductive turn-off, as verified in functional test Figure 1 with 7 mH load and 300 V clamp reference.

Is BU941ZP compatible with 24 V commercial vehicle ignition systems?

Yes. The 350 V V_CEO and 500 V clamping capability exceed typical 24 V system flyback voltages (<300 V). Functional testing confirms reliable operation at V_CC = 24 V with 7 mH load and 10 A peak current, meeting ISO 7637-2 pulse 5a requirements for commercial vehicle electrical environments.

BU941ZP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-247-3

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:: 2V @ 300mA, 12A

Current - Collector Cutoff (Max):: 100µA

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

Power - Max:: 155 W

Frequency - Transition:: -

Operating Temperature:: 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-247-3

BU941ZP FAQ

1.How can I place an order for BU941ZP through Aetrix?

Please submit a Request for Quotation (RFQ) for BU941ZP 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 BU941ZP reliable?

The price and inventory of BU941ZP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU941ZP is usually 5 days.

3.What payment methods are accepted for BU941ZP?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU941ZP transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BU941ZP?

BU941ZP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BU941ZP 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 BU941ZP?

For technical support, including BU941ZP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU941ZP requirements.

6.How does Aetrix verify that BU941ZP is sourced from the original manufacturer or authorized distributors?

All BU941ZP 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 BU941ZP meets industry standards.

7.What is the process for return or replacement of BU941ZP?

All BU941ZP units undergo pre-shipment inspection (PSI). If there is an issue with BU941ZP, 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 BU941ZP part is unused and in its original packaging.

Return procedure for BU941ZP:

1.Submit a request within 90 days.

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

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