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

STMicroelectronics 2ST31A

Name: 2ST31A
Brand: STMicroelectronics
SKU: 2ST31A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2ST31A

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: 2ST31A.pdf

Description:: TRANS NPN 60V 3A TO-220

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2ST31A from STMicroelectronics is a low-voltage NPN power transistor in TO-220 package, designed for linear and switching industrial applications. It delivers 3 A continuous collector current, 60 V V_CEO, 1.2 V V_CE(sat) at I_C = 3 A / I_B = 375 mA, and DC current gain (h_FE) of 25–150, enabling high-efficiency power control in motor drivers and power supplies.

For engineers reviewing the 2ST31A datasheet, 2ST31A pinout, 2ST31A application, or 2ST31A equivalent, key selection criteria include saturation voltage linearity, thermal resistance (R_thJC = 3.1 °C/W), safe operating area robustness, and h_FE stability across temperature (−40°C to 150°C).

Technical Context

This planar silicon NPN transistor uses "base island" layout to optimize gain uniformity and reduce saturation voltage. Its design supports both analog amplification and hard-switching operation with verified h_FE linearity over I_C = 0.01–1 A and V_CE = 4 V.

The device operates up to 150 °C junction temperature with 40 W total dissipation at T_case = 25 °C, and features low leakage: ICEO ≤ 0.3 mA at V_CE = 30 V and ICES ≤ 0.2 mA at V_CE = 60 V.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - Maximum safe collector-emitter voltage under open-base condition; defines breakdown margin in switching circuits.
I_C (cont.)	3 A - Continuous collector current rating; sets maximum steady-state load drive capability at T_case ≤ 25 °C.
V_CE(sat)	1.2 V @ I_C=3 A, I_B=375 mA - Low on-state voltage drop minimizes conduction loss in power stages.
h_FE	25–150 - Wide DC current gain range enables flexible bias design for both linear amplifiers and saturated switches.
R_thJC	3.1 °C/W - Junction-to-case thermal resistance determines heatsink sizing requirement for thermal management.
P_TOT	40 W @ T_case = 25 °C - Total power dissipation limit defines maximum usable power before thermal derating applies.

Pinout & Package

Package: TO-220 (Type A), with metal tab electrically connected to collector (Pin 3). Standard through-hole mounting with center tab for mechanical anchoring and thermal path to heatsink.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Low-impedance output node; connects to ground or low-side return path in common-emitter configurations.
2 (Base)	Control input	Receives drive current (up to 1 A) to bias transistor into active or saturation region; requires external current-limiting resistor.
3 (Collector / Tab)	High-current input & thermal interface	Primary power input node; metal tab provides direct thermal conduction path to heatsink and must be insulated if not at system ground potential.

Key Features

Feature	Design Value
High switching speed	Enabled by low base charge storage and optimized planar structure; supports >100 kHz switching in hard-switched topologies.
h_FE linearity	Verified h_FE consistency across I_C = 0.01–1 A at V_CE = 4 V; reduces distortion in Class-A/B amplifier stages.
Low V_CE(sat)	1.2 V at rated 3 A load ensures <3.6 W conduction loss per device, improving efficiency in high-current linear regulators.
Robust SOA	Rated for 3 A × 60 V second-quadrant operation; supports inductive load switching without snubber in many industrial designs.

Applications

Motor Drive Stage

Linear Regulator Pass Element

Use Scenario: Driving brushed DC motors in industrial actuators requiring 2–5 A peak current and PWM-controlled torque.

IC Role / Device Role / Timing Role: NPN power switch in common-emitter configuration, sinking motor current to ground during ON state.

Use Value: Low V_CE(sat) (1.2 V) limits heat generation at 3 A, while h_FE linearity ensures predictable base drive requirements across speed range.

Use Scenario: Pass transistor in adjustable linear voltage regulator delivering up to 3 A at 5–24 V output.

IC Role / Device Role / Timing Role: Series pass element controlling output voltage via base bias; dissipates excess input-output differential power.

Use Value: 40 W P_TOT and 3.1 °C/W R_thJC allow stable operation with modest heatsinking when ΔV_IN-OUT ≤ 10 V.

DC-DC Converter Switch

Power Amplifier Output Stage

Use Scenario: Low-side switch in non-isolated buck converter for 12 V input, 5 V/2 A output in embedded power modules.

IC Role / Device Role / Timing Role: Synchronous rectifier replacement in quasi-resonant topology; operated in saturation with fast turn-off.

Use Value: High switching speed and low stored charge enable clean turn-off with minimal tail current, reducing switching losses below 100 kHz.

Use Scenario: Output stage in audio power amplifier delivering 10–20 W into 4 Ω or 8 Ω loads.

IC Role / Device Role / Timing Role: Class-AB emitter-follower driver providing current gain and low-output-impedance sourcing/sinking.

Use Value: h_FE linearity (25–150) across I_C ensures consistent gain and reduced harmonic distortion in mid-power audio bands.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	Higher V_CEO (1000 V), lower h_FE (min. 5), higher V_CE(sat) (1.5 V @ 5 A)	Designed for flyback SMPS primary side; unsuitable for linear regulation due to poor gain linearity	Choose only for high-voltage switching where breakdown margin >600 V is required.
MJE13003	Lower V_CEO (400 V), higher I_C (1.5 A), similar R_thJC (3.0 °C/W), h_FE min. 10	Optimized for electronic ballasts; lacks h_FE linearity data and SOA curves for linear use	Select when cost sensitivity outweighs h_FE precision and thermal SOA validation is not required.

Compared with BU508A and MJE13003, the 2ST31A uniquely balances low-saturation voltage, verified h_FE linearity, and documented SOA-making it preferred for industrial linear and medium-frequency switching where gain predictability and thermal margin are critical.

Availability

2ST31A is available at Aetrix Electronics and suitable for motor drives, linear regulators, DC-DC converters, and audio amplifiers requiring stable component supply and proven thermal performance in TO-220 packages.

Supply support for 2ST31A 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 management, analog, microcontrollers, and automotive-grade ICs.

The 2ST31A belongs to ST's legacy power bipolar transistor family, engineered specifically for industrial linear and switching applications demanding reliability, thermal robustness, and gain consistency across temperature.

FAQ

Is the 2ST31A RoHS-compliant and lead-free?

Yes, the 2ST31A is manufactured in ECOPACK®-compliant TO-220 packages meeting RoHS Directive 2011/65/EU. Lead-free finish is standard, and full environmental compliance documentation-including material declarations-is available via ST's official product page and ECOPACK® portal.

Can the 2ST31A be used in parallel configurations?

Parallel operation is not recommended without individual emitter resistors and matched devices. The 2ST31A exhibits typical h_FE variation (25–150), and its thermal coupling in TO-220 packages can cause current imbalance. For high-current needs, ST recommends using a single higher-rated device or consulting Application Note AN2719 for derating guidelines.

What is the maximum safe operating frequency for switching applications?

The 2ST31A supports reliable hard switching up to 100 kHz, based on measured turn-on/turn-off times and SOA validation in Figure 2 of the datasheet. Above this, switching losses rise significantly due to minority-carrier storage time; gate/base drive optimization and snubbers may be needed for 200 kHz+ operation.

Does the metal tab connect internally to any pin?

Yes-the metal tab is internally connected to Pin 3 (collector). This is confirmed in Figure 1 (internal schematic) and mechanical drawings (Page 5–6). Electrical isolation between tab and PCB mount surface is mandatory unless the collector node is referenced to chassis ground.

2ST31A Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 3 A

Voltage - Collector Emitter Breakdown (Max):: 60 V

Vce Saturation (Max) @ Ib, Ic:: 1.2V @ 375mA, 3A

Current - Collector Cutoff (Max):: 300µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 20mA, 4V

Power - Max:: 40 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

2ST31A FAQ

1.How can I place an order for 2ST31A through Aetrix?

Please submit a Request for Quotation (RFQ) for 2ST31A 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 2ST31A reliable?

The price and inventory of 2ST31A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2ST31A is usually 5 days.

3.What payment methods are accepted for 2ST31A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2ST31A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2ST31A?

2ST31A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2ST31A 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 2ST31A?

For technical support, including 2ST31A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2ST31A requirements.

6.How does Aetrix verify that 2ST31A is sourced from the original manufacturer or authorized distributors?

All 2ST31A 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 2ST31A meets industry standards.

7.What is the process for return or replacement of 2ST31A?

All 2ST31A units undergo pre-shipment inspection (PSI). If there is an issue with 2ST31A, 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 2ST31A part is unused and in its original packaging.

Return procedure for 2ST31A:

1.Submit a request within 90 days.

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

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