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

STMicroelectronics 2STF1550

Name: 2STF1550
Brand: STMicroelectronics
SKU: 2STF1550
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2STF1550

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: 2STF1550.pdf

Description:: TRANS NPN 50V 5A SOT-89-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,207

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Product details

Overview

2STF1550 from STMicroelectronics is a low-voltage, high-performance NPN power transistor in SOT-89 package, featuring V_CE(sat) = 0.26 V at I_C = 3 A / I_B = 300 mA, h_FE ≥ 135 at I_C = 0.5 A, and P_TOT = 1.4 W at T_amb = 25 °C. It serves as a medium-power switching element in LED drivers and voltage regulation circuits.

For engineers reviewing the 2STF1550 datasheet, 2STF1550 pinout, 2STF1550 application, or 2STF1550 equivalent, this page delivers verified electrical ratings, thermal resistance (R_thj-amb = 89 °C/W), PB-HCD process advantages, and real-world use cases in battery chargers and motherboard power stages.

Technical Context

The 2STF1550 employs ST's proprietary "PB-HCD" (Power Bipolar High Current Density) technology to achieve simultaneous high DC current gain and ultra-low saturation voltage. Its design targets continuous conduction in medium-power linear and switching applications where thermal efficiency and base drive economy are critical.

Rated for V_CEO = 50 V and I_C = 5 A (I_CM = 10 A pulsed), it operates up to T_J = 150 °C with R_thj-amb = 89 °C/W on 1 cm² PCB copper area - enabling compact board-level thermal management without heatsinks in many portable designs.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	50 V - supports operation in 24 V and 36 V DC systems with margin against transients
I_C	5 A continuous - suitable for driving high-brightness LED strings or small solenoids
V_CE(sat)	0.26 V @ 3 A/300 mA - reduces conduction loss to < 0.78 W, easing thermal design
h_FE	≥135 @ 0.5 A - enables low-base-drive-current control from microcontroller GPIOs
P_TOT	1.4 W @ 25 °C ambient - defines maximum steady-state power dissipation on standard FR4
R_thj-amb	89 °C/W - quantifies junction-to-ambient thermal path on minimal 1 cm² copper pad
t_on/t_off	90 ns / 700 ns - supports PWM dimming up to ~1 MHz in LED backlighting

Pinout & Package

SOT-89 package: 3-pin surface-mount plastic case with exposed collector tab for thermal conduction. Pin 1 = emitter, Pin 2 = base, Pin 3 = collector (tab). Mounting requires minimum 1 cm² copper area for rated power dissipation.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Reference node for base-emitter bias; connects to ground or low-side return path
Pin 2	Base	Control input requiring ~300 mA drive for full saturation at 3 A collector current
Pin 3	Collector	Main power output terminal; electrically and thermally connected to exposed metal tab

Key Features

Feature	Design Value
Low V_CE(sat)	0.26 V minimizes I²R losses and self-heating during sustained conduction
High h_FE	135–400 range allows direct MCU GPIO drive without external pre-driver stage
Fast switching	90 ns turn-on enables efficient PWM control in LED and DC-DC applications
PB-HCD process	Enables high current density while maintaining bipolar reliability and SOA integrity
ECOPACK® compliance	Lead-free second-level interconnect meets JEDEC JESD97 and RoHS requirements

Applications

LED Driver

Battery Charger

Use Scenario: Constant-current switching driver for multi-chip white LED arrays in emergency lighting fixtures.

IC Role / Device Role / Timing Role: NPN power switch controlling LED string current via PWM-modulated base drive.

Use Value: Low V_CE(sat) maintains >92% efficiency at 3 A load; fast t_on ensures clean dimming response.

Use Scenario: Linear pass transistor in 5 V/3 A USB-C PD adapter secondary-side regulation.

IC Role / Device Role / Timing Role: Medium-power series pass element adjusting output voltage under microcontroller feedback loop.

Use Value: High h_FE reduces base drive burden; 1.4 W rating supports continuous operation without heatsink.

Motherboard Power Stage

Mobile Equipment Load Switch

Use Scenario: +12 V rail enable switch for HDD spindle motor or PCIe slot auxiliary power.

IC Role / Device Role / Timing Role: High-gain NPN used in Darlington configuration to drive 5 A loads from 3.3 V logic.

Use Value: V_CEO = 50 V provides margin against back-EMF; SOT-89 footprint saves board space vs TO-220.

Use Scenario: Load switch for camera module or display backlight in smartphone mainboard.

IC Role / Device Role / Timing Role: Discrete power switch replacing integrated load switches where cost and BOM simplification are prioritized.

Use Value: ECOPACK® compliance meets mobile OEM environmental requirements; 700 ns t_off prevents shoot-through in sequenced power-up.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD122G	V_CE(sat) = 0.5 V @ 3 A - 92% higher conduction loss than 2STF1550	Higher thermal demand limits use in space-constrained mobile PCBs	Prefer when legacy design reuse or wider V_CEO (80 V) is required
ZTX851	h_FE = 100 min @ 1 A - lower gain increases base drive requirement	Requires external driver stage for 3 A loads, increasing component count	Choose for cost-sensitive industrial controls where 1.6 W P_TOT suffices

Compared with MJD122G and ZTX851, the 2STF1550 delivers superior conduction efficiency and single-stage drive capability - making it optimal for thermally constrained, high-efficiency LED and portable power applications where base drive simplicity matters.

Availability

2STF1550 is available at Aetrix Electronics and suitable for LED driver modules, battery charger reference designs, and motherboard power sequencing requiring stable component supply across production lifecycles.

Supply support for 2STF1550 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 devices for industrial, automotive, and consumer markets.

The 2STF1550 belongs to ST's PB-HCD bipolar power transistor family, engineered specifically for high-efficiency, medium-power linear and switching applications where low saturation voltage and high current gain are simultaneously required.

FAQ

What is the maximum safe operating current for continuous DC conduction?

The 2STF1550 is rated for I_C = 5 A continuous at T_amb = 25 °C with adequate PCB copper area (1 cm²). At elevated ambient temperatures or reduced copper, derating applies per R_thj-amb = 89 °C/W - e.g., max I_C drops to ~3.2 A at 60 °C ambient assuming same thermal layout.

Can the 2STF1550 replace a MOSFET in low-side switching applications?

It can function as a low-side switch but differs fundamentally: bipolar operation requires sustained base current (~300 mA at 3 A I_C), unlike MOSFET gate charge. Use only where base drive capability exists and where its low V_CE(sat) justifies higher drive power versus MOSFET gate losses.

Is the SOT-89 package lead-free and RoHS compliant?

Yes - the 2STF1550 carries ST's ECOPACK® marking, indicating lead-free second-level interconnect and full compliance with RoHS Directive 2011/65/EU and JEDEC Standard JESD97. The inner box label specifies soldering profile limits.

How does PB-HCD technology improve performance over standard bipolar processes?

PB-HCD optimizes doping profiles and epitaxial layer structure to increase current density while reducing base resistance and collector series resistance. This yields both higher h_FE and lower V_CE(sat) - a trade-off traditionally difficult to achieve in conventional bipolar fabrication.

2STF1550 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-243AA

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 5 A

Voltage - Collector Emitter Breakdown (Max):: 50 V

Vce Saturation (Max) @ Ib, Ic:: 450mV @ 300mA, 3A

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 135 @ 2A, 2V

Power - Max:: 1.4 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-89-3

2STF1550 FAQ

1.How can I place an order for 2STF1550 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2STF1550 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 2STF1550 reliable?

The price and inventory of 2STF1550 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2STF1550 is usually 5 days.

3.What payment methods are accepted for 2STF1550?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2STF1550 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2STF1550?

2STF1550 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2STF1550 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 2STF1550?

For technical support, including 2STF1550 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2STF1550 requirements.

6.How does Aetrix verify that 2STF1550 is sourced from the original manufacturer or authorized distributors?

All 2STF1550 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 2STF1550 meets industry standards.

7.What is the process for return or replacement of 2STF1550?

All 2STF1550 units undergo pre-shipment inspection (PSI). If there is an issue with 2STF1550, 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 2STF1550 part is unused and in its original packaging.

Return procedure for 2STF1550:

1.Submit a request within 90 days.

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

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