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

STMicroelectronics STL128DN

Name: STL128DN
Brand: STMicroelectronics
SKU: STL128DN
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STL128DN

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: STL128DN.pdf

Description:: TRANS NPN 400V 4A TO-220

Quantity:: RFQ Add To RFQ list

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Product details

Overview

STL128DN from STMicroelectronics is a high-voltage fast-switching NPN power transistor with integrated antiparallel collector-emitter diode, rated for V_CES = 700 V, I_C = 4 A, and R_thJC = 2.08 °C/W (TO-220). It delivers very high switching speed (t_s = 4.5 µs, t_f = 0.4 µs) and large reverse-biased safe operating area (RBSOA), targeting electronic ballasts and low-power flyback/forward SMPS.

For engineers reviewing the STL128DN datasheet, STL128DN pinout, STL128DN application, or STL128DN equivalent, key selection criteria include its 700 V blocking capability, integrated freewheel diode (V_F = 2.5 V @ 1 A), low saturation voltage (V_CE(sat) = 0.5 V @ 1 A/0.2 A), and thermal performance in TO-220, TO-220FP, and DPAK packages.

Technical Context

The STL128DN employs high-voltage multi-epitaxial planar technology with cellular emitter structure and planar edge termination to simultaneously enhance switching speed and maintain wide RBSOA. Its integrated antiparallel diode enables self-contained freewheeling in single-transistor topologies without external diode placement.

Designed for hard-switched lighting and low-cost SMPS, it operates with V_CEO = 400 V at I_C = 10 mA and supports pulse collector currents up to 8 A (t_P < 5 ms), while maintaining stable h_FE = 10–24 across I_C = 10 mA to 2 A at V_CE = 5 V.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	700 V - Enables use in 230 VAC mains-fed flyback converters with sufficient margin against voltage spikes.
I_C (continuous)	4 A - Supports output power up to ~40 W in low-cost single-transistor forward converters.
t_s/t_f	4.5 µs / 0.4 µs - Enables switching frequencies >100 kHz with minimal turn-off losses in ballast drivers.
V_CE(sat)	0.5 V @ 1 A/0.2 A - Reduces conduction loss to <0.5 W at rated current, easing thermal design.
V_F (diode)	2.5 V @ 1 A - Integrated diode eliminates external component count and layout complexity in flyback snubberless designs.
R_thJC (TO-220)	2.08 °C/W - Allows 60 W dissipation at T_C = 25 °C, supporting compact heatsink solutions.
h_FE	10–24 - Provides predictable base drive requirements across operating range for stable BJT biasing.

Pinout & Package

STL128DN is available in three thermally optimized packages: TO-220 (standard through-hole), TO-220FP (full-pack, insulated tab), and TO-252 (DPAK, surface-mount). All variants feature identical pinout: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter, with metal tab electrically connected to Collector.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Base)	Control input	Receives current-driven signal (I_B ≤ 2 A) to saturate or cut off the transistor; requires external base resistor for current limiting.
Pin 2 (Collector)	High-side power node	Connected to primary winding or HV rail; carries full load current and withstands 700 V transient stress; tab is electrically tied to this terminal.
Pin 3 (Emitter)	Power return path	Serves as common reference for base drive and load current return; placed adjacent to base for low-inductance gate loop in switching layouts.

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates need for external freewheel diode in flyback snubberless topologies, reducing BOM count and PCB area.
Large RBSOA	Supports reliable operation under inductive switching stress without secondary breakdown, critical for lamp ignition surges in electronic ballasts.
Low dynamic parameter spread	Ensures consistent timing and gain behavior across production lots, simplifying factory calibration and batch testing.
ECOPACK® compliance	Meets RoHS and halogen-free requirements per ST's environmental packaging standards, enabling global market access.

Applications

Electronic Ballast Driver

Flyback SMPS

Use Scenario: Driving resonant LC network to ignite and regulate fluorescent lamps in commercial lighting fixtures.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling primary current in series-resonant half-bridge topology; integrates freewheel path during dead time.

Use Value: 700 V rating accommodates lamp ignition spikes; fast t_f = 0.4 µs minimizes switching loss during high-frequency (25–65 kHz) operation.

Use Scenario: Primary-side switch in isolated 12–24 W AC/DC adapters for consumer electronics.

IC Role / Device Role / Timing Role: Single-transistor flyback switch with integrated diode enabling snubberless operation and simplified transformer design.

Use Value: V_CE(sat) = 0.5 V reduces conduction loss; R_thJC = 2.08 °C/W allows TO-220 mounting on small heatsinks without forced air.

Forward Converter

LED Driver (HV Buck)

Use Scenario: Main power switch in cost-sensitive 30–40 W offline forward converters for industrial control power supplies.

IC Role / Device Role / Timing Role: Hard-switched NPN transistor handling DC-link voltage and delivering regulated output via transformer-coupled secondary.

Use Value: I_CM = 8 A peak supports startup surge; h_FE stability ensures predictable base drive across temperature and load.

Use Scenario: High-side switch in non-isolated buck-derived LED drivers for streetlight modules powered directly from rectified 230 VAC.

IC Role / Device Role / Timing Role: Constant-current regulator using linear or PWM-controlled conduction in high-voltage buck configuration.

Use Value: V_CEO(sus) = 400 V sustains continuous conduction mode under line transients; integrated diode provides path for inductor current decay.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STP12NK60Z	MOSFET (600 V, 12 A), no integrated diode, lower gate drive complexity but higher conduction loss above 1 A.	Requires external freewheel diode; better suited for higher-frequency (>200 kHz), lower-power (<15 W) applications.	Select when gate-drive simplicity and zero reverse recovery loss outweigh need for integrated diode and ruggedness at high dV/dt.
BU508A	Discrete NPN (1500 V, 8 A), no integrated diode, wider SOA but slower switching (t_f ≈ 1.2 µs).	Used in legacy TV horizontal deflection; lacks integrated diode and modern thermal specs; obsolete in new designs.	Consider only for drop-in replacement in legacy repair; not recommended for new energy-efficient lighting or SMPS designs.

Compared with STL128DN, STP12NK60Z offers superior high-frequency efficiency but increases component count and layout sensitivity, while BU508A trades switching speed and integration for raw voltage headroom-making STL128DN optimal for cost-sensitive, medium-power, diode-integrated lighting and SMPS where RBSOA and thermal robustness are prioritized.

Availability

STL128DN is available at Aetrix Electronics and suitable for electronic ballasts, flyback converters, forward converters, and high-voltage LED drivers requiring stable component supply and long-term industrial availability.

Supply support for STL128DN 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 consumer markets.

The STL128DN belongs to ST's high-voltage bipolar power transistor family, engineered specifically for cost-effective, robust switching in lighting and low-power offline power conversion where integration, ruggedness, and thermal reliability are essential.

FAQ

What package options are offered for STL128DN?

STL128DN is manufactured in three industry-standard packages: TO-220 (tube), TO-220FP (tube, insulated tab), and TO-252/DPAK (tape-and-reel). All share identical pinout (Base–Collector–Emitter) and electrical specifications; thermal resistance differs per package (2.08 °C/W for TO-220, 6.25 °C/W for DPAK).

Does STL128DN require a base resistor, and what value is typical?

Yes-STL128DN is a current-driven BJT and requires an external base resistor to limit I_B. For I_C = 2 A and h_FE = 10, I_B ≈ 200 mA; with V_BE(sat) = 1.3 V and 5 V drive, R_B ≈ 18 Ω (1/2 W minimum). Values must be recalculated based on actual drive voltage and target overdrive ratio.

Can STL128DN replace BU2520DX in electronic ballast designs?

No-BU2520DX is a 1500 V, 10 A NPN with different gain, SOA, and switching characteristics. STL128DN's 700 V rating and faster t_f suit modern 230 VAC ballasts, but it lacks the voltage margin required for BU2520DX's legacy CRT deflection applications. Direct substitution may cause premature failure under high-voltage transients.

Is the integrated diode rated for continuous freewheel current?

Yes-the integrated antiparallel diode is rated for I_F = 1 A continuous (V_F = 2.5 V), matching the transistor's I_C rating. It is designed for repetitive freewheeling in flyback and forward topologies, with thermal coupling to the same die ensuring synchronized junction temperature tracking.

STL128DN Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 4 A

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 400mA, 2A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 10 @ 10mA, 5V

Power - Max:: 60 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

STL128DN FAQ

1.How can I place an order for STL128DN through Aetrix?

Please submit a Request for Quotation (RFQ) for STL128DN 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 STL128DN reliable?

The price and inventory of STL128DN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STL128DN is usually 5 days.

3.What payment methods are accepted for STL128DN?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STL128DN transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STL128DN?

STL128DN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STL128DN 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 STL128DN?

For technical support, including STL128DN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STL128DN requirements.

6.How does Aetrix verify that STL128DN is sourced from the original manufacturer or authorized distributors?

All STL128DN 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 STL128DN meets industry standards.

7.What is the process for return or replacement of STL128DN?

All STL128DN units undergo pre-shipment inspection (PSI). If there is an issue with STL128DN, 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 STL128DN part is unused and in its original packaging.

Return procedure for STL128DN:

1.Submit a request within 90 days.

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

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