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

STMicroelectronics 2ST5949

Name: 2ST5949
Brand: STMicroelectronics
SKU: 2ST5949
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2ST5949

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: 2ST5949.pdf

Description:: TRANS NPN 250V 17A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:8,485

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Product details

Overview

2ST5949 from STMicroelectronics is a high-power NPN epitaxial planar bipolar transistor designed for linear audio power amplification, featuring V_CEO = 250 V, I_C = 17 A, P_TOT = 250 W at T_C = 25 °C, f_T = 25 MHz, and R_thj-case = 0.7 °C/W - deployed in TO-3 metal package for high-current, high-voltage output stages.

For engineers reviewing the 2ST5949 datasheet, 2ST5949 pinout, 2ST5949 application, or 2ST5949 equivalent, key selection considerations include safe operating area (SOA) at 125 °C, gain linearity under large-signal conditions, complementary pairing with 2ST2121, and thermal derating above 25 °C case temperature.

Technical Context

This device employs ST's BiT-LA (Bipolar transistor for linear amplifier) process to optimize gain linearity and reduce harmonic distortion in Class AB audio output stages. It is fully characterized up to T_C = 125 °C and supports pulsed collector currents up to 34 A (t_P < 5 ms).

The transistor exhibits V_CE(sat) = 3 V at I_C = 8 A / I_B = 800 mA and h_FE = 35–160 across I_C = 1–7 A, enabling stable biasing and predictable current drive in discrete power amplifier topologies.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	250 V - supports rail voltages up to ±100 V in push-pull audio output stages without breakdown
I_C	17 A continuous - delivers high output current into low-impedance speaker loads (e.g., 4 Ω, 8 Ω)
P_TOT	250 W at T_C = 25 °C - requires robust heatsinking; derates linearly above 25 °C per Figure 3
f_T	25 MHz - sufficient for full-audio bandwidth (20 Hz–20 kHz) with margin for stability compensation
R_thj-case	0.7 °C/W - enables junction temperature control when mounted on ≥100 cm² aluminum heatsink with thermal interface
h_FE	35–160 (I_C = 1–7 A) - supports stable DC bias design across production spread and temperature
V_CE(sat)	3 V @ I_C = 8 A - limits conduction loss and thermal stress in Class AB quiescent operation

Pinout & Package

Delivered in TO-3 metal package with electrically isolated collector tab (Case = Collector), standard three-terminal configuration: Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector (tab). Mounting hole centered for mechanical stability and thermal transfer.

Pin/Terminal	Circuit Role	Design Meaning
Base	Current-controlled input terminal	Accepts ~800 mA base drive to saturate 8 A collector current; requires low-impedance driver stage
Emitter	Common reference node for output stage	Connected to ground or negative rail; carries full load current and must be routed with low-inductance path
Collector (Tab)	Main power output terminal	Electrically connected to metal case; must be insulated from heatsink unless circuit topology requires common-collector mounting

Key Features

Feature	Design Value
BiT-LA process technology	Optimized for gain linearity and low THD in audio amplifiers - reduces second- and third-harmonic distortion at full output swing
High-temperature characterization	Fully specified at T_C = 125 °C - ensures reliable SOA and gain behavior in enclosed, thermally constrained enclosures
Complementary pairing	Matched performance with 2ST2121 (PNP) - enables symmetrical push-pull output stage design with balanced thermal and gain tracking
ECOPACK® compliance	Lead-free second-level interconnect - meets RoHS requirements without compromising solder joint reliability or thermal performance

Applications

Hi-Fi Audio Amplifier

Professional PA Output Stage

Use Scenario: Discrete Class AB output stage in stereo integrated amplifier delivering 100 W RMS per channel into 8 Ω.

IC Role / Device Role / Timing Role: Main NPN output transistor handling positive half-cycle current delivery and thermal dissipation.

Use Value: V_CEO = 250 V and SOA curve support ±85 V rails; h_FE consistency minimizes bias drift across temperature.

Use Scenario: High-power monoblock amplifier for live sound reinforcement, driving 4 Ω low-Z loudspeakers.

IC Role / Device Role / Timing Role: Primary NPN switch in parallel-output configuration with forced-air cooling.

Use Value: I_C = 17 A and P_TOT = 250 W enable >200 W continuous output; R_thj-case = 0.7 °C/W allows predictable thermal design.

Tube-Emulation Guitar Amplifier

Industrial Audio Monitoring System

Use Scenario: Solid-state replacement for vacuum tube output stage in boutique guitar amp, requiring soft clipping and harmonic richness.

IC Role / Device Role / Timing Role: Linear-mode NPN device biased in Class A/AB to replicate tube-like transfer characteristics.

Use Value: BiT-LA process ensures gain linearity and low crossover distortion - critical for musical transient response and even-order harmonic generation.

Use Scenario: Rack-mounted broadcast monitor amplifier used in studio control rooms with 24/7 operation.

IC Role / Device Role / Timing Role: Reliability-critical output transistor in fault-tolerant dual-redundant design.

Use Value: T_J(max) = 150 °C and full 125 °C characterization ensure long-term stability; TO-3 mechanical robustness resists vibration and thermal cycling.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
2N3055	V_CEO = 60 V, f_T ≈ 3 MHz, P_TOT = 115 W - significantly lower voltage rating and bandwidth	Suitable only for ≤±35 V rails; inadequate for modern high-headroom audio designs	Select only for legacy repair or low-voltage (<60 V) industrial linear regulators
MJE15030	V_CEO = 250 V, I_C = 8 A, P_TOT = 150 W - lower current/power capability and no 125 °C characterization	Limited to medium-power amplifiers (≤50 W); lacks SOA data above 25 °C	Prefer where space constraints limit heatsink size but full 250 W is not required

Compared with 2N3055 and MJE15030, the 2ST5949 uniquely combines 250 V breakdown, 17 A current, 250 W dissipation, and full 125 °C specification - making it the only option among the three qualified for high-fidelity, high-rail, thermally demanding audio output stages.

Availability

2ST5949 is available at Aetrix Electronics and suitable for Hi-Fi audio amplifiers, professional PA systems, tube-emulation guitar amplifiers, and industrial audio monitoring systems requiring stable component supply despite its obsolete status through controlled legacy sourcing.

Supply support for 2ST5949 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 industrial, automotive, and consumer markets.

The 2ST5949 belongs to ST's high-power bipolar transistor family developed specifically for linear audio amplifier applications - emphasizing gain linearity, thermal robustness, and SOA integrity under real-world dynamic load conditions.

FAQ

Is the 2ST5949 still in active production?

No - STMicroelectronics declared the 2ST5949 obsolete in November 2008 (Rev 4). However, Aetrix Electronics maintains traceable inventory from authorized legacy channels and offers controlled distribution with full documentation and lot traceability for ongoing production and repair programs.

Can the 2ST5949 be used in switching applications?

It is not recommended. The 2ST5949 is optimized for linear operation (e.g., Class AB audio), with relatively high V_CE(sat) = 3 V and slow turn-off characteristics. Its SOA and thermal design target analog fidelity-not fast switching-making it unsuitable for SMPS or PWM motor drives.

What is the correct mounting orientation and insulation requirement?

The TO-3 collector tab is electrically connected to the collector terminal. When mounted to a heatsink, an insulating washer (e.g., mica or silicone pad) and shoulder washer must be used unless the circuit explicitly requires the collector to be at heatsink potential. Tighten mounting screw to 0.5–0.7 N·m to ensure thermal contact without cracking the package.

How does the 2ST5949 compare to modern MOSFET-based audio outputs?

Unlike power MOSFETs, the 2ST5949 offers superior linearity and lower gate-drive complexity in analog amplifiers but requires precise biasing and generates more heat at idle. Its BiT-LA process preserves sonic character valued in high-end audio, whereas MOSFETs excel in efficiency and ruggedness for high-power switching amplifiers.

2ST5949 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-204AA, TO-3

Packaging:: Bag

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 17 A

Voltage - Collector Emitter Breakdown (Max):: 250 V

Vce Saturation (Max) @ Ib, Ic:: 3V @ 800mA, 8A

Current - Collector Cutoff (Max):: 5µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 80 @ 1A, 5V

Power - Max:: 250 W

Frequency - Transition:: 25MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Chassis Mount

Supplier Device Package:: TO-3

2ST5949 FAQ

1.How can I place an order for 2ST5949 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2ST5949 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 2ST5949 reliable?

The price and inventory of 2ST5949 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2ST5949 is usually 5 days.

3.What payment methods are accepted for 2ST5949?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2ST5949 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2ST5949?

2ST5949 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2ST5949 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 2ST5949?

For technical support, including 2ST5949 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2ST5949 requirements.

6.How does Aetrix verify that 2ST5949 is sourced from the original manufacturer or authorized distributors?

All 2ST5949 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 2ST5949 meets industry standards.

7.What is the process for return or replacement of 2ST5949?

All 2ST5949 units undergo pre-shipment inspection (PSI). If there is an issue with 2ST5949, 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 2ST5949 part is unused and in its original packaging.

Return procedure for 2ST5949:

1.Submit a request within 90 days.

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

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