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

STMicroelectronics STW2040

Name: STW2040
Brand: STMicroelectronics
SKU: STW2040
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STW2040

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-247-3

Datasheet:: STW2040.pdf

Description:: TRANS NPN 500V 20A TO-247-3

Quantity:: RFQ Add To RFQ list

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Inventory:8,903

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Product details

Overview

STW2040 from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-247 package, rated for 500 V V_CEO, 20 A continuous collector current, and 125 W total dissipation at T_c = 25 °C; it delivers h_FE ≥ 15 at I_C = 6 A and exhibits t_on/t_f/t_s of 140 ns / 100 ns / 1.6 µs under resistive load switching - used in offline SMPS primary-side switching stages.

For engineers reviewing the STW2040 datasheet, STW2040 pinout, STW2040 application, or STW2040 equivalent, key selection criteria include V_CEO derating at elevated case temperature, safe operating area (SOA) compliance under inductive switching, base drive current requirements (I_B = 4 A for I_C = 20 A), and thermal resistance R_thJC ≤ 1 °C/W for heatsink design.

Technical Context

The STW2040 employs diffused collector planar technology with base island layout to achieve tight lot-to-lot parametric spread and stable h_FE across production batches. Its structure supports high-voltage blocking (V_CES = 700 V) while maintaining low V_CE(sat) (0.3 V typ. at I_C = 12 A, I_B = 2.4 A) and fast switching transitions.

It is optimized for hard-switched, non-resonant topologies where SOA robustness under inductive turn-off stress (V_CL = 250 V, t_s = 1.8 µs) and low storage time are critical - not intended for linear-mode operation or avalanche-rated applications.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	500 V - maximum collector-emitter voltage with base open; defines primary-side MOSFET replacement ceiling in 400 V DC bus SMPS
I_C	20 A - continuous DC collector current at T_c = 25 °C; sets minimum heatsink requirement for 300–500 W converters
V_CE(sat)	0.3 V (typ.) at I_C = 12 A, I_B = 2.4 A - directly determines conduction loss and junction temperature rise
h_FE	15–27 (I_C = 6–12 A, V_CE = 5 V) - enables predictable base drive sizing without active current limiting
t_s (inductive)	1.8 µs - storage time under V_CL = 250 V; limits maximum practical switching frequency to ≤ 100 kHz in flyback/forward designs
R_thJC	≤ 1 °C/W - junction-to-case thermal resistance; mandates direct mounting to copper heatsink with thermal interface material

Pinout & Package

TO-247 package: 3-pin through-hole outline with isolated metal tab (collector), standard lead pitch and mounting hole per mechanical drawing (A = 5.15 mm, D = 20.15 mm, L = 14.80 mm). Tab is electrically connected to collector.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input	Receives base drive current (I_B = 4 A typical for full saturation at I_C = 20 A); requires low-inductance path to driver
2 (Collector)	Main power output terminal	Connected to high-voltage DC bus (e.g., rectified AC line); electrically tied to metal tab - must be insulated from heatsink unless referenced to same potential
3 (Emitter)	Power return reference	Serves as common emitter node; carries full load current and must route to low-impedance ground plane to minimize switching noise coupling

Key Features

Feature	Design Value
High V_CEO rating	500 V enables direct use in universal-input (85–265 V_AC) offline SMPS without series stacking
Tight h_FE distribution	Lot-to-lot consistency reduces base drive design margin and improves batch yield in volume production
Low R_thJC	≤ 1 °C/W allows compact heatsink integration in space-constrained industrial power supplies
Fast storage time	1.6 µs (resistive) / 1.8 µs (inductive) supports efficient 50–100 kHz switching without excessive snubber losses

Applications

Offline Flyback Converter

DC-DC Forward Converter

Use Scenario: Primary-side switch in 100–300 W universal-input flyback power supply for industrial control modules.

IC Role / Device Role / Timing Role: High-voltage NPN transistor performing hard-switched on/off control of transformer primary winding; driven by UC384x-based controller.

Use Value: V_CEO = 500 V withstands reflected output voltage + leakage spike; SOA curve validated up to 250 V clamp level ensures reliability during overload.

Use Scenario: Main switching device in 200–400 W forward converter for telecom power shelf units.

IC Role / Device Role / Timing Role: Single-ended primary switch conducting full input current during ON-time; reset via tertiary winding.

Use Value: h_FE ≥ 15 at I_C = 12 A simplifies base drive design; low V_CE(sat) minimizes conduction loss at 50 kHz switching.

AC-DC Adapter Power Stage

Industrial Motor Drive Pre-regulator

Use Scenario: Primary switch in compact 65 W laptop adapter with integrated EMI filter and synchronous rectification.

IC Role / Device Role / Timing Role: Fast-switching NPN transistor handling 400 V DC bus; gate/base drive synchronized to PWM controller timing.

Use Value: t_f = 100 ns and t_s = 1.6 µs reduce switching transition losses; TO-247 package enables direct heatsink attachment for thermal management.

Use Scenario: Bulk DC link pre-regulator in 3-phase inverter drives for HVAC compressors.

IC Role / Device Role / Timing Role: High-current switch regulating intermediate DC bus voltage prior to IGBT inverter stage.

Use Value: I_C = 20 A rating supports 500 W continuous power; R_thJC ≤ 1 °C/W permits forced-air cooling instead of liquid cooling.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	V_CEO = 1000 V, I_C = 15 A, h_FE = 5–25, R_thJC = 1.5 °C/W	Higher voltage margin but lower current and higher thermal resistance	Preferred where V_in > 550 V DC or SOA demands wider voltage headroom
2SD1898	V_CEO = 400 V, I_C = 25 A, h_FE = 10–30, R_thJC = 0.8 °C/W	Lower voltage rating but higher current and better thermal performance	Selected when bus voltage ≤ 375 V DC and thermal budget is tighter than voltage margin

Compared with BU508A and 2SD1898, the STW2040 offers optimal balance of 500 V blocking, 20 A current, and 1 °C/W thermal resistance for mainstream 400 V DC bus SMPS - avoiding over-spec'd voltage (BU508A) or under-spec'd voltage (2SD1898) in typical industrial adapters.

Availability

STW2040 is available at Aetrix Electronics and suitable for offline switch-mode power supplies, industrial DC-DC converters, and AC-DC adapter power stages requiring stable component supply and long-term manufacturability assurance.

Supply support for STW2040 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, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for automotive, industrial, and power applications.

The STW2040 belongs to ST's high-voltage bipolar transistor product line, engineered specifically for ruggedized, cost-sensitive primary-side switching in offline power conversion systems up to 500 W.

FAQ

Is STW2040 still in active production?

No - STW2040 is marked "Obsolete Product(s)" in its official datasheet (Doc ID 15149 Rev 2, June 2009). STMicroelectronics discontinued this part; Aetrix Electronics provides remaining inventory with full traceability and extended support for legacy design continuity.

Can STW2040 replace a MOSFET in a flyback converter?

Yes, but with design adjustments: it requires ~4 A peak base drive (vs. gate charge in MOSFETs), lacks intrinsic body diode, and needs careful SOA validation under inductive turn-off. It is not a drop-in MOSFET replacement but a functionally equivalent high-voltage switch with different drive and protection requirements.

What is the maximum recommended case temperature for continuous operation?

The absolute maximum junction temperature is 150 °C, and R_thJC ≤ 1 °C/W implies that at 125 W dissipation, case temperature must stay ≤ 25 °C - thus derating is mandatory. At T_c = 100 °C, maximum allowable P_TOT drops to ~25 W per the derating curve in Figure 3 of the datasheet.

Does STW2040 support avalanche energy rating?

No - the datasheet does not specify avalanche energy (E_AS) or ruggedness testing. Its safe operating area is defined only for forward-biased conditions (Figure 2 and Figure 4); operation beyond SOA limits risks secondary breakdown and irreversible failure.

STW2040 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):: 20 A

Voltage - Collector Emitter Breakdown (Max):: 500 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 1.2A, 6A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 15 @ 6A, 5V

Power - Max:: 125 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-247-3

STW2040 FAQ

1.How can I place an order for STW2040 through Aetrix?

Please submit a Request for Quotation (RFQ) for STW2040 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 STW2040 reliable?

The price and inventory of STW2040 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STW2040 is usually 5 days.

3.What payment methods are accepted for STW2040?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STW2040 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STW2040?

STW2040 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STW2040 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 STW2040?

For technical support, including STW2040 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STW2040 requirements.

6.How does Aetrix verify that STW2040 is sourced from the original manufacturer or authorized distributors?

All STW2040 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 STW2040 meets industry standards.

7.What is the process for return or replacement of STW2040?

All STW2040 units undergo pre-shipment inspection (PSI). If there is an issue with STW2040, 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 STW2040 part is unused and in its original packaging.

Return procedure for STW2040:

1.Submit a request within 90 days.

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

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