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

STMicroelectronics 2STF1340

Name: 2STF1340
Brand: STMicroelectronics
SKU: 2STF1340
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2STF1340

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: 2STF1340.pdf

Description:: TRANS NPN 40V 3A SOT-89-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2STF1340 from STMicroelectronics is a low-voltage, fast-switching NPN power transistor fabricated with PB-HCD (Power Bipolar High Current Density) technology. It delivers V_CE(sat) = 250 mV at I_C = 2 A / I_B = 100 mA, h_FE = 450 (min) at I_C = 3 A, and f_T = 100 MHz, enabling high-efficiency switching in DC-DC converters and LED driver stages.

For engineers reviewing the 2STF1340 datasheet, 2STF1340 pinout, 2STF1340 application, or 2STF1340 equivalent, this device is selected for low-saturation, high-gain bipolar switching where thermal resistance (R_thJA = 89 °C/W on 1 cm² PCB) and fast turn-on/turn-off times (t_on = 65 ns, t_off = 750 ns) are critical in space-constrained power stages.

Technical Context

The 2STF1340 operates as a medium-power NPN switch optimized for linear and saturated-mode operation in non-isolated DC-DC topologies. Its PB-HCD process enables simultaneous high h_FE (up to 450) and low V_CE(sat) (250–350 mV), reducing conduction loss while maintaining robust gain stability across I_C = 0.1–3 A and T_J = –40 to 125 °C.

It features a complementary PNP counterpart (2STF2340), supports resistive-load switching per Figure 11 test circuit, and exhibits C_CB = 30 pF at V_CB = 10 V / f = 1 MHz - a key parameter for high-frequency switching noise control and snubber design.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CE(sat)	250 mV @ I_C = 2 A / I_B = 100 mA - enables <1 W conduction loss in 2 A load paths
h_FE	450 min @ I_C = 3 A / V_CE = 2 V - ensures stable base drive margin under high-current saturation
f_T	100 MHz @ I_C = 0.1 A / V_CE = 5 V - supports clean switching up to ~10 MHz practical operating frequency
t_on/t_off	65 ns / 750 ns @ resistive load - defines minimum pulse width and dead-time requirements in PWM stages
R_thJA	89 °C/W on 1 cm² PCB - sets thermal derating limit to ~1.1 W continuous at 70 °C ambient
V_CEO	40 V - suitable for 24 V nominal input DC-DC and LED string drivers with margin
I_C (cont)	3 A - supports >5 W output power in compact SOT-89 footprint without forced cooling

Pinout & Package

Supplied in SOT-89 package: surface-mount, 3-pin, single-ended power plastic case with exposed emitter pad for thermal enhancement. Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (as shown in Figure 1 internal schematic and mechanical drawing).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current return path and thermal reference node	Connected directly to PCB copper pour for heat dissipation; common reference for base drive
Pin 2 (Base)	Control input for minority-carrier injection	Requires current-limited drive (e.g., 100–150 mA) to achieve full saturation without overdrive
Pin 3 (Collector)	Main power output terminal	High-current path to load; electrically isolated from heatsink in SOT-89 mounting

Key Features

Feature	Design Value
Very low V_CE(sat)	250 mV at 2 A enables >95% efficiency in 5–12 V DC-DC buck stages
High h_FE linearity	h_FE ≥ 100 at I_C = 0.1 A and ≥ 220 at I_C = 3 A - reduces base drive complexity across load range
Fast switching	65 ns turn-on + 750 ns turn-off allows PWM operation up to 1 MHz with controlled overlap loss
PB-HCD process	Enables high current density (3 A in SOT-89) without thermal runaway or gain collapse

Applications

LED Driver Stage

DC-DC Converter Switch

Use Scenario: Constant-current switching stage driving multi-LED strings in portable backlight or indicator systems.

IC Role / Device Role / Timing Role: NPN power switch controlling LED current path in low-side configuration.

Use Value: Low V_CE(sat) minimizes voltage headroom loss, extending battery runtime; fast t_off prevents LED ghosting during PWM dimming.

Use Scenario: Main switching transistor in non-synchronous buck converter for 5–12 V rail generation.

IC Role / Device Role / Timing Role: Low-side power switch synchronizing with external diode or controller IC.

Use Value: High h_FE simplifies gate/base driver design; 40 V V_CEO supports 24 V input with safety margin.

Motherboard Power Sequencing

Hard Disk Drive Motor Control

Use Scenario: Enable/disable logic-controlled 3.3 V or 5 V auxiliary rails during system boot or sleep transitions.

IC Role / Device Role / Timing Role: Medium-current power switch activated by GPIO or PMIC signal.

Use Value: 3 A rating handles peak inrush of LDOs or small DC-DCs; SOT-89 footprint saves board area vs. TO-220.

Use Scenario: Spindle motor start-up current limiter and direction control interface in 2.5″ HDD designs.

IC Role / Device Role / Timing Role: High-gain switch interfacing between MCU GPIO and motor winding driver stage.

Use Value: Stable h_FE across temperature ensures consistent torque response; 150 °C T_Jmax withstands localized heating near motor coils.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BCP56-10T1G	V_CE(sat) = 500 mV @ I_C = 1 A - higher saturation loss; h_FE = 100–250 - lower gain linearity	Lower current rating (1 A) limits use to sub-2 W loads; slower switching (t_off ≈ 1.2 µs)	Select when cost sensitivity outweighs efficiency and thermal constraints
MJD112	TO-220 package - higher R_thJA (~65 °C/W with heatsink); V_CE(sat) = 1.5 V @ I_C = 2 A - significantly higher conduction loss	Requires heatsink for >1.5 A continuous; unsuitable for compact SOT-89 layouts	Choose only if legacy board design mandates through-hole mounting or >3 A pulsed capability

Compared with BCP56-10T1G and MJD112, the 2STF1340 provides superior combination of low-loss switching, high-current density in SOT-89, and wide h_FE linearity - making it optimal for thermally constrained, medium-power DC-DC and LED applications where board space and efficiency are prioritized.

Availability

2STF1340 is available at Aetrix Electronics and suitable for LED driver stages, motherboard power sequencing, and DC-DC converter switches requiring stable component supply and long-term industrial availability.

Supply support for 2STF1340 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 for automotive, industrial, and consumer markets.

The 2STF1340 belongs to ST's power bipolar transistor family, engineered specifically for high-efficiency, medium-current switching in compact surface-mount power supplies and lighting systems.

FAQ

Is the 2STF1340 RoHS-compliant and halogen-free?

Yes. The 2STF1340 is manufactured in ECOPACK®-compliant SOT-89 packaging, meeting RoHS Directive 2011/65/EU and halogen-free requirements per IEC 61249-2-21. Full compliance documentation is available via ST's quality portal using order code 2STF1340.

What is the maximum safe operating current at 85 °C ambient?

At T_amb = 85 °C with 1 cm² PCB copper, R_thJA = 89 °C/W limits junction temperature to 150 °C at P_diss = (150 − 85) / 89 ≈ 0.73 W. Using V_CE(sat) = 350 mV at I_C = 3 A, max continuous I_C ≈ √(0.73 / 0.35) ≈ 1.4 A for safe operation.

Can the 2STF1340 replace a MOSFET in low-side switching?

It can functionally replace low-voltage N-channel MOSFETs in non-critical, medium-speed applications, but requires base current drive (vs. voltage drive), exhibits higher V_CE(sat) than modern MOSFETs, and lacks inherent body diode. Use only where bipolar characteristics (e.g., gain-based current mirroring) are advantageous.

Does ST provide SPICE models for the 2STF1340?

No official SPICE model is published by ST for the 2STF1340. Designers should rely on datasheet curves (Figures 2–7) and empirical characterization for simulation. For behavioral modeling, use generic NPN parameters with h_FE = 350, V_CE(sat) = 0.3 V, and f_T = 100 MHz as starting points.

2STF1340 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):: 3 A

Voltage - Collector Emitter Breakdown (Max):: 40 V

Vce Saturation (Max) @ Ib, Ic:: 350mV @ 150mA, 3A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 180 @ 1A, 2V

Power - Max:: 1.4 W

Frequency - Transition:: 100MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-89-3

2STF1340 FAQ

1.How can I place an order for 2STF1340 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2STF1340 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 2STF1340 reliable?

The price and inventory of 2STF1340 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2STF1340 is usually 5 days.

3.What payment methods are accepted for 2STF1340?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2STF1340 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2STF1340?

2STF1340 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2STF1340 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 2STF1340?

For technical support, including 2STF1340 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2STF1340 requirements.

6.How does Aetrix verify that 2STF1340 is sourced from the original manufacturer or authorized distributors?

All 2STF1340 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 2STF1340 meets industry standards.

7.What is the process for return or replacement of 2STF1340?

All 2STF1340 units undergo pre-shipment inspection (PSI). If there is an issue with 2STF1340, 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 2STF1340 part is unused and in its original packaging.

Return procedure for 2STF1340:

1.Submit a request within 90 days.

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

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