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

STMicroelectronics STW3040

Name: STW3040
Brand: STMicroelectronics
SKU: STW3040
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STW3040

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-247-3

Datasheet:: STW3040.pdf

Description:: TRANS NPN 400V 30A TO-247-3

Quantity:: RFQ Add To RFQ list

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Inventory:2,258

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Product details

Overview

STW3040 from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-247 package, rated for 400 V V_CEO, 30 A continuous collector current, and 160 W total dissipation at T_c = 25°C; designed specifically for switching mode power supplies (SMPS) and desktop power supply main switch applications.

For engineers reviewing the STW3040 datasheet, STW3040 pinout, STW3040 application, or STW3040 equivalent, key selection criteria include V_CEO rating, h_FE linearity at 6–20 A, V_CE(sat) under pulsed drive, safe operating area (SOA) boundaries, and thermal resistance R_thj-case ≤ 0.78 °C/W.

Technical Context

The STW3040 employs diffused collector planar technology with base island layout to achieve wide forward and reverse-biased safe operating areas. Its DC current gain (h_FE) ranges from 10 to 40 across 10 mA–20 A, supporting stable linear and switching operation.

Switching performance is characterized by 0.5 µs turn-on time, 2.5 µs storage time, and 0.3 µs fall time under resistive load conditions (V_CC = 200 V, I_C = 20 A), enabling efficient high-frequency SMPS operation up to ~100 kHz.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - maximum collector-emitter voltage with base open; defines primary breakdown limit in SMPS flyback/forward topologies
I_C (cont.)	30 A - continuous collector current at T_c = 25°C; sets RMS current capability in hard-switched converters
P_TOT	160 W - total power dissipation at case temperature 25°C; determines heatsink sizing baseline
R_thj-case	≤ 0.78 °C/W - junction-to-case thermal resistance; enables direct thermal modeling for thermal design
V_CE(sat)	0.4 V @ I_C = 20 A, I_B = 4 A - low saturation voltage reduces conduction loss in high-current switching nodes
h_FE	18–30 @ I_C = 6–20 A - moderate, predictable DC gain supports stable base drive design without excessive overdrive
t_on/t_s/t_f	0.5 / 2.5 / 0.3 µs - fast switching timing enables high-efficiency operation in 50–100 kHz SMPS designs

Pinout & Package

TO-247 package: isolated metal tab (collector), 3-pin through-hole configuration with standard lead assignment per Figure 1. Mounting surface is electrically connected to collector.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives base current to enable conduction; requires ≥4 A peak drive for full 20 A switching
2 (Collector)	High-side power node	Connected to heatsink; carries full load current and withstands 400 V transient spikes
3 (Emitter)	Power return path	Low-inductance emitter connection critical for minimizing switching oscillation and gate drive loop area

Key Features

Feature	Design Value
Wide SOA (forward & reverse biased)	Enables reliable operation under inductive load transients and secondary-side rectifier snubbing without derating
Minimum lot-to-lot spread	Reduces need for binning or system-level margining in volume production of AC-DC adapters
ECOPACK® lead-free construction	Complies with RoHS and JEDEC JESD97 marking standards; supports lead-free reflow and wave soldering
High V_CES = 700 V	Provides headroom for voltage overshoot during turn-off in offline SMPS with 400 V DC bus

Applications

Desktop Power Supply Main Switch

Industrial SMPS Primary Switch

Use Scenario: High-efficiency 300–500 W ATX power supply primary-side switching transistor.

IC Role / Device Role / Timing Role: NPN power switch controlling energy transfer from bulk capacitor to transformer primary.

Use Value: 0.4 V V_CE(sat) at 20 A reduces conduction loss by >1.5 W vs. typical alternatives, improving 230 V full-load efficiency.

Use Scenario: 200–400 W industrial open-frame SMPS operating in harsh ambient (T_a ≤ 70°C).

IC Role / Device Role / Timing Role: Hard-switched primary-side transistor in forward converter topology.

Use Value: 0.78 °C/W R_thj-case allows use of compact extruded heatsink without forced air, reducing system size and cost.

UPS Inverter Stage

LED Driver Bulk Switch

Use Scenario: Line-interactive UPS output stage handling 120–240 VAC conversion with battery backup.

IC Role / Device Role / Timing Role: High-voltage switching element in half-bridge inverter leg.

Use Value: Reverse-biased SOA supports safe commutation during dead-time transitions without external clamping.

Use Scenario: High-power constant-current LED driver for street lighting (≥100 W).

IC Role / Device Role / Timing Role: Primary-side switch regulating bulk DC using PWM-controlled base drive.

Use Value: Stable h_FE from 10 mA to 20 A enables single-drive circuit architecture across dimming range without gain compensation.

Availability

STW3040 is available at Aetrix Electronics and suitable for switching mode power supplies, desktop power supplies, and industrial AC-DC converters requiring stable component supply and long-term BOM continuity.

Supply support for STW3040 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, digital, and mixed-signal ICs and discrete power devices for industrial, automotive, and consumer markets.

The STW3040 belongs to ST's high-voltage bipolar power transistor product line, engineered for robustness and thermal stability in mains-connected power conversion systems.

FAQ

Is STW3040 still in active production?

No - STW3040 is marked "Obsolete Product(s)" in the official ST datasheet (Rev 3, Oct 2008). It is no longer manufactured, but Aetrix Electronics maintains legacy inventory with full traceability and extended lifecycle support for existing designs.

What is the recommended base drive configuration for STW3040 in SMPS applications?

Drive with ≥4 A peak base current (I_B) for full 20 A collector conduction, using a low-impedance path and minimized loop inductance. A 1.2 Ω series base resistor with ±15 V drive is typical; ensure t_s ≤ 2.5 µs is accommodated in gate driver timing budget.

Can STW3040 replace STW20NK50Z in a flyback converter?

No - STW20NK50Z is a 500 V, 20 A N-channel MOSFET with logic-level gate drive; STW3040 is a 400 V NPN BJT requiring high-current base drive. They differ in control mechanism, voltage rating, and drive architecture - not functionally interchangeable.

Does STW3040 require a heatsink in continuous 20 A operation?

Yes - at 20 A and 0.4 V V_CE(sat), conduction loss is ~8 W. With R_thj-case = 0.78 °C/W, junction temperature rise exceeds 100°C even with minimal case-to-ambient resistance; a properly sized heatsink is mandatory for reliability.

STW3040 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-247-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 30 A

Voltage - Collector Emitter Breakdown (Max):: 400 V

Vce Saturation (Max) @ Ib, Ic:: 800mV @ 4A, 20A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 18 @ 6A, 5V

Power - Max:: 160 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-247-3

STW3040 FAQ

1.How can I place an order for STW3040 through Aetrix?

Please submit a Request for Quotation (RFQ) for STW3040 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 STW3040 reliable?

The price and inventory of STW3040 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STW3040 is usually 5 days.

3.What payment methods are accepted for STW3040?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STW3040 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STW3040?

STW3040 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STW3040 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 STW3040?

For technical support, including STW3040 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STW3040 requirements.

6.How does Aetrix verify that STW3040 is sourced from the original manufacturer or authorized distributors?

All STW3040 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 STW3040 meets industry standards.

7.What is the process for return or replacement of STW3040?

All STW3040 units undergo pre-shipment inspection (PSI). If there is an issue with STW3040, 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 STW3040 part is unused and in its original packaging.

Return procedure for STW3040:

1.Submit a request within 90 days.

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

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