Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

STMicroelectronics BU941ZT

Name: BU941ZT
Brand: STMicroelectronics
SKU: BU941ZT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: BU941ZT

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BU941ZT.pdf

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

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:2,351

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

BU941ZT from STMicroelectronics is a high-voltage NPN power Darlington transistor designed for electronic ignition coil driving, featuring 350 V V_CEO, 15 A continuous collector current, built-in clamping Zener (V_CL = 350–500 V), and 175 °C maximum junction temperature. It operates in automotive ignition systems with inductive loads up to 7 mH and 10 A peak.

For engineers reviewing the BU941ZT datasheet, BU941ZT pinout, BU941ZT application, or BU941ZT equivalent, key selection criteria include clamped inductive switching capability, rugged thermal performance in D2PAK/TO-220 packages, safe operating area under pulsed inductive stress, and base-drive compatibility with 47 Ω R_BE and 70 mA I_B.

Technical Context

This Darlington device integrates a monolithic NPN output transistor with an internal Zener diode across C–E for voltage clamping during inductive turn-off, eliminating external snubbers in ignition circuits. Its DC current gain (h_FE ≥ 300 at I_C = 5 A) enables low-base-current drive while sustaining 1.8 V V_CE(sat) at 8–10 A.

Thermal design relies on its 1 °C/W R_thj-case in TO-220 and 2.7 °C/W in D2PAK, supporting 150 W P_tot at T_C = 25 °C. Switching is characterized by 15 µs storage time and 0.5 µs fall time under defined inductive test conditions (V_CC = 12 V, L = 7 mH, I_C = 7 A).

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Withstands ignition coil back-EMF without external clamp
I_C (continuous)	15 A - Sustains full primary current of high-energy ignition systems
V_CL	350–500 V - Integrated Zener limits voltage spike during inductive turn-off
V_CE(sat)	1.8 V @ 8 A / 100 mA I_B - Minimizes conduction loss and heat generation
h_FE	≥300 @ I_C = 5 A - Enables efficient base drive with low control current
T_j(max)	175 °C - Supports operation in under-hood automotive environments
R_thj-case (TO-220)	1 °C/W - Allows high-power dissipation with minimal heatsink requirement

Pinout & Package

BU941ZT is available in through-hole TO-220 and surface-mount D2PAK (TO-263) packages. The TO-220 variant uses standard 3-pin configuration with emitter (pin 1), base (pin 2), and collector (pin 3) - collector internally connected to tab for direct heatsinking.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current return path	Low-impedance emitter connection; referenced to ground in common-emitter ignition driver
Pin 2 (Base)	Control input	Receives current-limited drive (e.g., via 47 Ω resistor) to saturate Darlington pair
Pin 3 (Collector)	High-side load switch node	Connected to ignition coil primary; carries full load current and clamped flyback voltage

Key Features

Feature	Design Value
Integrated clamping Zener	Eliminates need for external transient voltage suppressor in ignition coil drivers
175 °C max junction temperature	Enables reliable operation in engine compartment without derating at elevated ambient
150 W total dissipation (T_C = 25 °C)	Supports high-duty-cycle ignition pulses without thermal shutdown
300 minimum h_FE	Reduces required base drive current and driver-stage component count
15 µs storage time	Ensures fast turn-off recovery in repetitive spark timing applications

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 Darlington switch controlling spark timing via microcontroller PWM or discrete trigger signals.

Use Value: Built-in clamping eliminates external TVS, reducing BOM count and PCB area while ensuring consistent 350–500 V flyback limiting.

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

IC Role / Device Role / Timing Role: Inductive load switch activated by PLC outputs or safety relays to ignite fuel-air mixtures.

Use Value: 175 °C T_j(max) and 15 A I_C support continuous duty cycles in high-ambient industrial enclosures without forced cooling.

Motorcycle Ignition Control

Aftermarket Ignition Upgrades

Use Scenario: Compact ignition module for dual-cylinder motorcycle engines with space-constrained mounting.

IC Role / Device Role / Timing Role: Surface-mount D2PAK version (BU941ZT) used as main switching element in miniaturized ECU designs.

Use Value: D2PAK package provides 2.7 °C/W thermal resistance and solderable heatsink pad, enabling direct PCB thermal management.

Use Scenario: Retrofit electronic ignition kits replacing points-based systems in classic vehicles.

IC Role / Device Role / Timing Role: Drop-in Darlington driver interfacing legacy distributor signals with modern high-energy coils.

Use Value: Pin-compatible TO-220 footprint and 350 V V_CEO ensure compatibility with existing harnesses and coil specifications.

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
STGD10NB60KD	600 V, 10 A N-channel MOSFET with integrated gate driver; no internal Zener clamp	Requires external clamping network; faster switching but higher gate drive complexity	Preferred for high-frequency digital ignition where precise timing control outweighs simplicity
TIP122G	100 V V_CEO, 5 A I_C, no integrated Zener; lower thermal rating (T_j = 150 °C)	Insufficient for 350 V ignition flyback; requires external clamp and larger heatsink	Suitable only for low-energy or 12 V battery-sourced inductive loads, not automotive primary ignition

Compared with STGD10NB60KD and TIP122G, BU941ZT uniquely combines 350 V clamping, 15 A current handling, and 175 °C operation in a single-package Darlington solution-reducing system-level protection components and simplifying thermal design for legacy and cost-sensitive ignition platforms.

Availability

BU941ZT is available at Aetrix Electronics and suitable for automotive ignition systems, industrial burner controls, motorcycle ECU modules, and aftermarket ignition upgrades requiring stable component supply and long-term manufacturability.

Supply support for BU941ZT 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 solutions for automotive, industrial, and consumer markets.

BU941ZT belongs to ST's high-voltage bipolar power transistor family, engineered specifically for rugged, high-energy inductive switching in automotive and industrial ignition applications.

FAQ

What is the function of the built-in Zener diode in BU941ZT?

The integrated Zener diode clamps the collector-emitter voltage to 350–500 V during inductive turn-off, protecting the transistor from destructive flyback spikes generated by ignition coils. It replaces external transient voltage suppressors, reducing component count and layout complexity in ignition driver circuits.

Can BU941ZT be used in surface-mount designs?

Yes - the BU941ZT is offered in D2PAK (TO-263) package, which supports surface-mount assembly. Its exposed collector tab allows direct thermal connection to PCB copper planes or heatsinks, delivering 2.7 °C/W thermal resistance when properly mounted.

What base drive configuration is recommended for optimal switching?

A 47 Ω series resistor between driver and base (pin 2) is specified in the functional test circuit, with 70 mA base current. This ensures saturation while limiting base charge storage, minimizing storage time (15 µs) and enabling clean turn-off in repetitive spark applications.

How does BU941ZT compare to standard power transistors in ignition use?

Unlike generic power transistors, BU941ZT integrates clamping, guarantees 175 °C operation, and is characterized for inductive switching (ts = 15 µs, tf = 0.5 µs). Its 300 h_FE and 1.8 V V_CE(sat) reduce driver losses and simplify interface design versus lower-gain alternatives like TIP122.

BU941ZT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Last Time Buy

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:: Automotive

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BU941ZT FAQ

1.How can I place an order for BU941ZT through Aetrix?

Please submit a Request for Quotation (RFQ) for BU941ZT 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 BU941ZT reliable?

The price and inventory of BU941ZT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU941ZT is usually 5 days.

3.What payment methods are accepted for BU941ZT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU941ZT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BU941ZT?

BU941ZT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BU941ZT 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 BU941ZT?

For technical support, including BU941ZT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU941ZT requirements.

6.How does Aetrix verify that BU941ZT is sourced from the original manufacturer or authorized distributors?

All BU941ZT 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 BU941ZT meets industry standards.

7.What is the process for return or replacement of BU941ZT?

All BU941ZT units undergo pre-shipment inspection (PSI). If there is an issue with BU941ZT, 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 BU941ZT part is unused and in its original packaging.

Return procedure for BU941ZT:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-03 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-01 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…

2026-08-14 Jumper Cables: How to Use, Connect and Choose Them Safely

Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…