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

onsemi BUT12ATU

Name: BUT12ATU
Brand: onsemi
SKU: BUT12ATU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: BUT12ATU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BUT12ATU.pdf

Description:: TRANS NPN 450V 8A TO-220-3

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:3,785

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

Product details

Overview

BUT12ATU from ON Semiconductor (formerly Fairchild) is an NPN silicon power transistor designed for high-voltage switching in inductive load circuits, with V_CEO = 450 V, I_C = 8 A DC, P_C = 100 W at T_C = 25°C, and TO-220 package mounting. It serves as a main switch in flyback converters, motor drivers, and solenoid controls where rugged turn-off and voltage standoff are critical.

For engineers reviewing the BUT12ATU datasheet, pinout, applications, or equivalent options, key selection criteria include sustained collector-emitter voltage rating under inductive switching, pulse current capability (I_CP = 20 A), saturation voltage at rated drive (V_CE(sat) = 1.5 V @ I_C = 6 A, I_B = 1.2 A), and thermal performance in forced-air or heatsink-mounted configurations.

Technical Context

The BUT12ATU operates as a single NPN bipolar junction transistor optimized for high-voltage, medium-current switching. Its design emphasizes robust secondary breakdown immunity and controlled storage time (t_STG = 4 µs) to support reliable operation in snubberless inductive turn-off.

It features a V_CEO(sus) of 400 V under standardized inductive test conditions (I_C = 100 mA, L = 25 mH), confirming its suitability for unclamped inductive switching. Base-emitter and collector-base breakdown ratings (V_EBO = 9 V, V_CBO = 1000 V) further define safe drive and blocking margins.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	450 V - Maximum continuous collector-emitter voltage before breakdown; enables use in 400 V bus applications with safety margin.
I_C (DC)	8 A - Continuous collector current rating; defines steady-state power handling with appropriate heatsinking.
P_C	100 W - Total collector dissipation at case temperature 25°C; sets thermal design baseline for TO-220 mounting.
V_CE(sat)	1.5 V @ I_C = 6 A, I_B = 1.2 A - Low saturation voltage reduces conduction loss and self-heating during on-state.
t_STG	4 µs - Storage time determines minimum off-time required before retriggering; critical for PWM frequency limits in inductive loads.
T_J	150°C - Maximum junction temperature; constrains allowable thermal resistance from junction-to-case and case-to-ambient.
V_CBO	1000 V - Collector-base breakdown voltage; supports gate-drive isolation integrity and voltage transient tolerance.

Pinout & Package

Package: TO-220 (3-lead, straight lead, insulated tab). Mounting surface is electrically isolated from collector terminal. Standard through-hole footprint with 2.54 mm lead pitch.

Pin/Terminal	Circuit Role	Design Meaning
1 (Left)	Base	Current-controlled input node; requires ≥1.2 A peak base drive for full saturation at 6 A collector current.
2 (Center)	Collector	Main high-side switching node; connected to heatsink via insulated mounting; carries full load current and voltage stress.
3 (Right)	Emitter	Reference node for base drive and load return path; low-inductance connection essential for fast switching stability.

Key Features

Feature	Design Value
High V_CEO(sus)	400 V under inductive switching - Enables snubberless operation in relay and solenoid drivers without external clamping.
Controlled t_STG/t_F	4 µs storage + 0.8 µs fall time - Supports clean turn-off in 20–50 kHz PWM ranges for magnetic actuator control.
Robust secondary breakdown	Rated for unclamped inductive switching per JEDEC JESD24 - Reduces need for overdesign in flyback and boost converter primary switches.
Isolated TO-220 tab	Electrically insulated collector mounting surface - Simplifies heatsink integration without additional insulators or thermal pads.

Applications

Switch-Mode Power Supply Primary Switch	AC Solenoid Driver
Use Scenario: Used as main switching transistor in 50–200 W offline flyback converters with 375 V DC bus. IC Role / Device Role / Timing Role: High-voltage NPN switch controlling energy transfer into transformer primary; handles repetitive 450 V reverse bias and 8 A peak current. Use Value: V_CEO = 450 V and V_CEO(sus) = 400 V allow direct replacement of older 400 V parts without snubber redesign.	Use Scenario: Drives 24–120 V AC solenoids in industrial valve control with zero-crossing triggered firing. IC Role / Device Role / Timing Role: Line-synchronized switching element turning AC half-cycles on/off; withstands 1.4× RMS line voltage transients. Use Value: 1000 V V_CBO and 150°C T_J ensure reliability during repeated inrush and hold-current cycling.
DC Motor Commutation Stage	Ignition Coil Driver
Use Scenario: Controls armature current in brushed 24–48 V DC motors used in material handling equipment. IC Role / Device Role / Timing Role: Low-side switching transistor in H-bridge or single-ended configuration; commutates inductive back-EMF spikes. Use Value: I_CP = 20 A pulse rating accommodates motor stall currents without second breakdown failure.	Use Scenario: Triggers primary winding discharge in automotive or small-engine ignition systems. IC Role / Device Role / Timing Role: Fast-turn-off switch interrupting 3–5 A primary current to induce high-voltage spark in secondary. Use Value: t_STG = 4 µs and t_F = 0.8 µs enable precise spark timing control within narrow dwell windows.

Switch-Mode Power Supply Primary Switch

AC Solenoid Driver

Use Scenario: Used as main switching transistor in 50–200 W offline flyback converters with 375 V DC bus.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling energy transfer into transformer primary; handles repetitive 450 V reverse bias and 8 A peak current.

Use Value: V_CEO = 450 V and V_CEO(sus) = 400 V allow direct replacement of older 400 V parts without snubber redesign.

Use Scenario: Drives 24–120 V AC solenoids in industrial valve control with zero-crossing triggered firing.

IC Role / Device Role / Timing Role: Line-synchronized switching element turning AC half-cycles on/off; withstands 1.4× RMS line voltage transients.

Use Value: 1000 V V_CBO and 150°C T_J ensure reliability during repeated inrush and hold-current cycling.

DC Motor Commutation Stage

Ignition Coil Driver

Use Scenario: Controls armature current in brushed 24–48 V DC motors used in material handling equipment.

IC Role / Device Role / Timing Role: Low-side switching transistor in H-bridge or single-ended configuration; commutates inductive back-EMF spikes.

Use Value: I_CP = 20 A pulse rating accommodates motor stall currents without second breakdown failure.

Use Scenario: Triggers primary winding discharge in automotive or small-engine ignition systems.

IC Role / Device Role / Timing Role: Fast-turn-off switch interrupting 3–5 A primary current to induce high-voltage spark in secondary.

Use Value: t_STG = 4 µs and t_F = 0.8 µs enable precise spark timing control within narrow dwell windows.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	V_CEO = 1000 V, I_C = 15 A, P_C = 125 W, TO-218 package	Higher voltage rating and power dissipation; larger footprint and thermal mass	Preferred when >600 V bus or >10 A peak current is required; requires PCB layout revision.
2SD1762	V_CEO = 400 V, I_C = 8 A, P_C = 80 W, TO-220 package, faster t_F = 0.5 µs	Slightly lower voltage margin and power rating; improved switching speed	Valid alternative where 400 V V_CEO suffices and faster turn-off is prioritized over ruggedness.

Compared with BU508A and 2SD1762, the BUT12ATU offers balanced voltage headroom (450 V), proven inductive switching robustness, and TO-220 compatibility-making it optimal for cost-sensitive, thermally constrained 400 V-class power switching where reliability under transient overload is critical.

Availability

BUT12ATU is available at Aetrix Electronics and suitable for industrial motor drives, AC/DC power supplies, electromagnetic actuator controls, and ignition system designs requiring stable component supply across multi-year production cycles.

Supply support for BUT12ATU 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

ON Semiconductor (acquired Fairchild Semiconductor in 2016) is a global supplier of energy-efficient semiconductor components focused on power management, analog, sensor, and logic solutions.

The BUT12ATU belongs to Fairchild's legacy high-voltage bipolar power transistor family, engineered specifically for rugged, cost-effective switching in industrial and appliance-grade inductive load control.

FAQ

What is the maximum continuous collector current rating for BUT12ATU?

The BUT12ATU has a maximum continuous collector current (I_C) rating of 8 A at case temperature T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C per the specified thermal resistance curve. The BUT12ATU must not exceed this limit in DC or high-duty-cycle applications to avoid thermal runaway or secondary breakdown.

Does BUT12ATU support snubberless inductive switching?

Yes, the BUT12ATU supports snubberless inductive switching, validated by its V_CEO(sus) = 400 V rating under standardized test conditions (I_C = 100 mA, L = 25 mH). This specification confirms its ability to safely absorb inductive energy without external clamping components-critical for reliable operation in relay drivers and flyback converters using the BUT12ATU.

What is the pin configuration of BUT12ATU in the TO-220 package?

The BUT12ATU uses a standard TO-220 package with 3 leads in left-to-right order: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter. The metal tab is electrically connected to the collector and is insulated from the mounting surface. This pinout is consistent across Fairchild's BUT12/BUT12A series and verified in the original August 2001 datasheet for BUT12ATU.

Can BUT12ATU replace BUT12 in existing designs?

Yes, the BUT12ATU is a direct replacement for the BUT12 in most applications, offering identical pinout and package but with higher V_CEO (450 V vs. 400 V) and V_CBO (1000 V vs. 850 V). No PCB changes are needed; however, designers should verify that increased voltage margin does not affect gate-drive timing or base resistor sizing in marginal drive conditions for the BUT12ATU.

What is the typical V_CE(sat) of BUT12ATU at rated current?

The typical V_CE(sat) of BUT12ATU is 1.5 V at I_C = 6 A and I_B = 1.2 A, as specified in the August 2001 Fairchild datasheet. This value reflects the device's low on-state loss under full drive, directly impacting conduction efficiency and thermal design. Actual V_CE(sat) may vary ±0.2 V across temperature and unit-to-unit; the BUT12ATU datasheet provides min/typ/max curves for design margining.

BUT12ATU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 8 A

Voltage - Collector Emitter Breakdown (Max):: 450 V

Vce Saturation (Max) @ Ib, Ic:: 1.5V @ 1.2A, 6A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: -

Power - Max:: 100 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220-3

BUT12ATU FAQ

1.How can I place an order for BUT12ATU through Aetrix?

Please submit a Request for Quotation (RFQ) for BUT12ATU 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 BUT12ATU reliable?

The price and inventory of BUT12ATU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUT12ATU is usually 5 days.

3.What payment methods are accepted for BUT12ATU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUT12ATU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUT12ATU?

BUT12ATU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUT12ATU 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 BUT12ATU?

For technical support, including BUT12ATU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUT12ATU requirements.

6.How does Aetrix verify that BUT12ATU is sourced from the original manufacturer or authorized distributors?

All BUT12ATU 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 BUT12ATU meets industry standards.

7.What is the process for return or replacement of BUT12ATU?

All BUT12ATU units undergo pre-shipment inspection (PSI). If there is an issue with BUT12ATU, 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 BUT12ATU part is unused and in its original packaging.

Return procedure for BUT12ATU:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 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…

2026-09-02 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…