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 STL128DNFP

Name: STL128DNFP
Brand: STMicroelectronics
SKU: STL128DNFP
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: STL128DNFP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3 Full Pack

Datasheet:: STL128DNFP.pdf

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

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:5,684

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

Product details

Overview

STL128DNFP from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-220FP package, rated for V_CES = 700 V, I_C = 4 A, and P_TOT = 28 W at T_c = 25 °C, with integrated antiparallel collector-emitter diode and t_s = 4.5 µs storage time. It is engineered for electronic ballasts and low-power flyback/forward SMPS.

For engineers reviewing the STL128DNFP datasheet, STL128DNFP pinout, STL128DNFP application, or STL128DNFP equivalent, key selection factors include its 700 V blocking capability, 4.5 µs resistive-load storage time, R_thJC = 4.46 °C/W thermal resistance, and suitability for lighting and cost-sensitive offline converters.

Technical Context

This device uses high-voltage multi-epitaxial planar technology with cellular emitter structure and planar edge termination to simultaneously achieve high switching speed and wide RBSOA. Its integrated freewheel diode (V_F = 2.5 V at I_F = 1 A) eliminates external diode requirements in flyback topologies.

The transistor supports sustained operation up to T_J = 150 °C with V_CEO(sus) = 400 V at I_C = 10 mA and exhibits tight dynamic parameter distribution-critical for consistent performance across production batches in lighting control circuits.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	700 V - enables direct connection to 230 VAC mains after bridge rectification without additional voltage clamping
I_C	4 A continuous - supports up to ~60 W output in single-transistor forward converters
t_s	4.5 µs - reduces switching losses in 20–65 kHz ballast and SMPS designs
R_thJC	4.46 °C/W - defines heatsink requirement for 28 W dissipation at case temperature ≤25 °C
V_F (diode)	2.5 V @ 1 A - lowers conduction loss during freewheeling phase in flyback snubberless operation
h_FE	10–24 @ I_C = 10 mA to 2 A - supports base-driven operation without complex current-sense feedback

Pinout & Package

STL128DNFP is housed in TO-220FP package (insulated tab), with three terminals: Collector (Tab), Base (Pin 1), Emitter (Pin 2). Pin 3 is not connected. The insulated tab allows direct mounting to heatsink without electrical isolation hardware.

Pin/Terminal	Circuit Role	Design Meaning
Tab	Collector	High-current, high-voltage main terminal; electrically connected to heatsink via insulated mounting
Pin 1	Base	Current-controlled input node; requires 0.2–0.4 A drive for full saturation at 1–2 A collector current
Pin 2	Emitter	Reference node for base drive and load return path; carries full load current in common-emitter configuration

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates discrete diode in flyback snubberless designs, reducing BOM count and PCB area
Large RBSOA	Supports reliable operation under inductive switching stress without secondary breakdown in 400 V bus applications
Low spread of dynamic parameters	Enables consistent timing and loss behavior across units-critical for mass-produced lighting ballasts
High voltage capability (700 V)	Permits use in universal-input (90–264 VAC) offline converters without derating or series stacking

Applications

Electronic Ballast Control

Flyback SMPS

Use Scenario: Driving resonant LC tank in instant-start fluorescent lamp ballasts operating at 20–60 kHz.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling lamp current waveform and ignition pulse generation.

Use Value: Integrated diode enables self-oscillating topology; 700 V rating withstands lamp open-circuit transients.

Use Scenario: Primary-side switch in 10–30 W isolated AC/DC adapters for consumer electronics.

IC Role / Device Role / Timing Role: Main energy-transfer switch in discontinuous conduction mode (DCM) flyback converter.

Use Value: 4.5 µs storage time minimizes switching loss at 50 kHz; 28 W dissipation supports compact heatsinking.

Forward Converter

LED Driver (HV Buck)

Use Scenario: Single-transistor forward converter for industrial control power supplies (12–24 V output).

IC Role / Device Role / Timing Role: Main switch synchronizing with transformer reset; operates with external freewheel diode or integrated diode.

Use Value: Wide RBSOA ensures robustness during core saturation events; 4 A rating supports >20 W output.

Use Scenario: High-side buck switch driving constant-current LED strings directly from rectified 230 VAC.

IC Role / Device Role / Timing Role: High-voltage series pass element in non-isolated buck topology with passive current regulation.

Use Value: 700 V V_CES accommodates peak line voltage + margin; integrated diode provides path for inductor current decay.

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
STP12NK60Z	600 V, 12 A MOSFET; R_DS(on) = 0.6 Ω; gate-driven, no integrated diode	Requires external freewheel diode; lower gate drive complexity but higher conduction loss at low duty cycles	Prefer when zero-voltage switching or synchronous rectification is used; avoid if diode integration is mandatory
BU508A	1500 V, 8 A BJT; no integrated diode; slower switching (t_s ≈ 10 µs); TO-218 package	Higher voltage margin but larger footprint and higher switching loss at >30 kHz	Choose only for ultra-high-voltage legacy designs where 700 V is insufficient; not suitable for compact ballasts

Compared with STL128DNFP, STP12NK60Z offers higher current and voltage-rated MOSFET operation but lacks integrated diode and demands gate driver design; BU508A provides greater voltage headroom but sacrifices switching speed and board space efficiency.

Availability

STL128DNFP is available at Aetrix Electronics and suitable for electronic ballasts, flyback SMPS, forward converters, and non-isolated LED drivers requiring stable component supply and long-lifecycle support.

Supply support for STL128DNFP 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, specializing in power, analog, MEMS, and microcontroller technologies for industrial, automotive, and consumer markets.

The STL128DNFP belongs to ST's high-voltage bipolar power transistor family, designed specifically for cost-effective, high-reliability lighting and low-power offline power conversion where integrated diode functionality and tight dynamic parameter distribution are essential.

FAQ

Is STL128DNFP pin-compatible with STL128DN?

Yes-both share identical pinout (Collector/Tab, Base/Pin 1, Emitter/Pin 2) and mechanical outline, but STL128DNFP features an insulated tab (TO-220FP) versus conductive tab (TO-220), eliminating need for insulating washers when mounted to grounded heatsinks.

What is the maximum recommended operating frequency for STL128DNFP?

Based on t_s = 4.5 µs and t_f = 0.4 µs, the device is optimized for 20–65 kHz operation in lighting and SMPS applications; above 100 kHz, switching losses increase significantly due to finite minority-carrier lifetime in bipolar structure.

Can STL128DNFP replace BU2508DF in electronic ballasts?

Yes-both are 700 V NPN transistors with integrated diodes in TO-220FP packages; STL128DNFP offers tighter h_FE spread and improved RBSOA, making it suitable for high-volume ballast production where consistency and reliability are critical.

Does STL128DNFP require a base resistor in standard switching configurations?

Yes-a base resistor is required to limit I_B to ≤2 A peak and ensure proper saturation; for I_C = 2 A, typical design uses I_B = 0.4 A, implying R_B ≈ (V_drive − 1.3 V)/0.4 A, assuming V_BE(sat) = 1.3 V per datasheet.

STL128DNFP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3 Full Pack

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:: 8 @ 2A, 5V

Power - Max:: 28 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220FP

STL128DNFP FAQ

1.How can I place an order for STL128DNFP through Aetrix?

Please submit a Request for Quotation (RFQ) for STL128DNFP 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 STL128DNFP reliable?

The price and inventory of STL128DNFP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STL128DNFP is usually 5 days.

3.What payment methods are accepted for STL128DNFP?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STL128DNFP transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STL128DNFP?

STL128DNFP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STL128DNFP 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 STL128DNFP?

For technical support, including STL128DNFP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STL128DNFP requirements.

6.How does Aetrix verify that STL128DNFP is sourced from the original manufacturer or authorized distributors?

All STL128DNFP 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 STL128DNFP meets industry standards.

7.What is the process for return or replacement of STL128DNFP?

All STL128DNFP units undergo pre-shipment inspection (PSI). If there is an issue with STL128DNFP, 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 STL128DNFP part is unused and in its original packaging.

Return procedure for STL128DNFP:

1.Submit a request within 90 days.

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

Tech Hub

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…

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…