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

STMicroelectronics BU941P

Name: BU941P
Brand: STMicroelectronics
SKU: BU941P
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BU941P

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-247-3

Datasheet:: BU941P.pdf

Description:: TRANS NPN DARL 400V 15A TO-247-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BU941P from STMicroelectronics is an NPN power Darlington transistor with integrated antiparallel collector-emitter diode, rated for 500 V V_CES, 15 A continuous collector current, and 200 °C maximum junction temperature, designed for high-ruggedness electronic ignition coil driving in automotive and industrial systems.

For engineers reviewing the BU941P datasheet, BU941P pinout, BU941P application, or BU941P equivalent, key selection criteria include V_CES = 500 V, I_C = 15 A, R_thj-case = 0.97 °C/W (TO-3), integrated flyback diode, and T_j(max) = 200 °C - critical for inductive switching reliability in ignition systems.

Technical Context

This Darlington device uses rugged bipolar technology optimized for high-voltage inductive load switching. It features a monolithically integrated antiparallel diode to clamp inductive kickback, supports pulsed operation up to 30 A peak collector current, and maintains stable gain (h_FE ≥ 300 at I_C = 5 A) across wide temperature ranges.

The device operates with low saturation voltages (V_CE(sat) = 1.6–2.0 V at I_C = 8–12 A / I_B = 100–300 mA) and fast switching performance (t_s = 15 µs, t_f = 0.5 µs under specified inductive test conditions), enabling efficient energy transfer in ignition coil drivers.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	500 V - Withstands full ignition coil primary voltage transients without breakdown.
I_C (continuous)	15 A - Sustains steady-state coil energization current in 12 V/24 V automotive systems.
R_thj-case	0.97 °C/W (TO-3) - Enables high-power dissipation with minimal thermal rise when mounted on heatsink.
V_CE(sat)	1.6 V @ I_C = 8 A, I_B = 100 mA - Minimizes conduction loss and self-heating during active drive phase.
h_FE	≥300 @ I_C = 5 A, V_CE = 10 V - Ensures robust base drive efficiency and low control current requirement.
T_j(max)	200 °C - Supports operation in high-ambient under-hood environments without derating.
Integrated Diode	Antiparallel C–E - Eliminates need for external flyback diode, reducing BOM count and layout area.

Pinout & Package

BU941P is supplied in TO-3 metal package: collector connected to mounting tab, emitter on pin 2, base on pin 1. The tab serves as both mechanical anchor and primary thermal path to heatsink.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Base	Low-impedance input for TTL/CMOS-compatible driver stages; requires ≤1 A peak base current.
Pin 2	Emitter	Return path for load current; referenced to ground or negative rail in common-emitter configuration.
Tab	Collector	High-current output node and primary thermal interface; electrically isolated mounting required if chassis-grounded.

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates discrete flyback diode, reduces PCB footprint and assembly cost in ignition modules.
200 °C max junction temperature	Enables reliable operation in engine bay environments exceeding 125 °C ambient without thermal shutdown.
0.97 °C/W thermal resistance	Allows >150 W dissipation at ΔT = 150 °C, supporting high-duty-cycle coil firing.
V_CEO(sus) = 400 V	Guarantees controlled clamping during inductive turn-off, preventing destructive voltage overshoot.
Fast storage time (15 µs)	Reduces dwell time overhead, enabling precise spark timing control up to 10,000 RPM.

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-voltage, high-current switch controlling coil energization and collapse timing.

Use Value: Integrated diode and 500 V rating prevent voltage runaway during rapid coil de-energization, ensuring consistent spark generation.

Use Scenario: Controlling spark plugs in gas-fired industrial burners and furnaces.

IC Role / Device Role / Timing Role: Robust power switch interfacing with microcontroller-based flame management logic.

Use Value: 200 °C T_j(max) and 15 A rating support continuous duty in high-temperature combustion enclosures.

Motorcycle Ignition Units

Aftermarket Ignition Controllers

Use Scenario: Compact CDI (capacitor discharge ignition) output stage in two-wheeler ECU designs.

IC Role / Device Role / Timing Role: Final-stage Darlington delivering high peak current pulses to ignition coil.

Use Value: Low V_CE(sat) minimizes power loss in space-constrained units where heatsinking is limited.

Use Scenario: Replacement or upgrade component in programmable ignition timing boxes.

IC Role / Device Role / Timing Role: Drop-in compatible high-ruggedness switch replacing legacy discrete Darlington pairs.

Use Value: Monolithic integration improves reliability over multi-component solutions subject to solder joint fatigue.

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
BU941	Same die, but rated for T_j(max) = 200 °C and P_tot = 180 W (vs. BU941P's 155 W); identical pinout and electrical specs.	Preferred where higher continuous power dissipation is needed and thermal design allows.	Select BU941 when system-level thermal margin exceeds 25 W above BU941P's rating.
BUB941PFI	Same package and pinout, but T_j(max) = 175 °C and P_tot = 65 W; lower R_thj-case = 2.3 °C/W due to ISOWATT218 package.	Suitable for lower-power, surface-mount–compatible layouts where TO-3 mounting is impractical.	Choose BUB941PFI only when board space constraints prohibit TO-3 and peak power < 65 W.

Compared with BU941 and BUB941PFI, BU941P delivers optimal balance of ruggedness (200 °C T_j), power handling (155 W), and proven TO-3 mechanical reliability - making it the preferred choice for production automotive ignition modules requiring long-term field stability.

Availability

BU941P is available at Aetrix Electronics and suitable for automotive ignition systems, industrial burner controls, and motorcycle CDI units requiring stable component supply and long-lifecycle availability.

Supply support for BU941P 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 microcontroller products for industrial, automotive, and consumer markets.

BU941P belongs to ST's high-voltage power bipolar transistor family, engineered specifically for ruggedized inductive switching in automotive ignition and industrial arc-generation systems.

FAQ

What is the recommended gate/base drive circuit for BU941P in ignition applications?

BU941P requires a low-impedance base driver capable of delivering ≥300 mA peak current (e.g., using a dedicated Darlington driver IC or MOSFET buffer). A 47 Ω base resistor is typical for TTL-level control; base-emitter clamping with a 5.1 V Zener prevents reverse bias damage during inductive flyback.

Can BU941P be used in parallel for higher current capability?

No - BU941P lacks built-in emitter ballasting resistors and exhibits positive thermal feedback. Parallel operation risks current hogging and thermal runaway. For >15 A, use a single higher-rated device (e.g., ST's STGF10NC60KD) or redesign with forced-air cooling.

Is the integrated diode rated for continuous forward conduction?

No - the antiparallel diode is optimized for transient clamping during inductive turn-off (pulse duration < 300 µs, duty cycle ≤1.5%). It is not rated for sustained forward current; external diodes must handle continuous freewheeling paths.

What is the maximum safe operating area (SOA) limit at 100 °C case temperature?

At T_c = 100 °C, the SOA boundary restricts simultaneous V_CE and I_C to ≤250 V × 6 A (DC) or ≤400 V × 2.5 A (pulsed, 300 µs). Derating curves in the official ST datasheet (page 2/8) must be consulted for precise pulse-width and duty-cycle limits.

BU941P 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):: 400 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

BU941P FAQ

1.How can I place an order for BU941P through Aetrix?

Please submit a Request for Quotation (RFQ) for BU941P 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 BU941P reliable?

The price and inventory of BU941P are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU941P is usually 5 days.

3.What payment methods are accepted for BU941P?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU941P transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BU941P?

BU941P orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BU941P 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 BU941P?

For technical support, including BU941P datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU941P requirements.

6.How does Aetrix verify that BU941P is sourced from the original manufacturer or authorized distributors?

All BU941P 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 BU941P meets industry standards.

7.What is the process for return or replacement of BU941P?

All BU941P units undergo pre-shipment inspection (PSI). If there is an issue with BU941P, 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 BU941P part is unused and in its original packaging.

Return procedure for BU941P:

1.Submit a request within 90 days.

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

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