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

STMicroelectronics 2N3771

Name: 2N3771
Brand: STMicroelectronics
SKU: 2N3771
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N3771

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: 2N3771.pdf

Description:: TRANS NPN 40V 30A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,223

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Product details

Overview

2N3771 from STMicroelectronics is a high-power silicon NPN epitaxial-base transistor in a TO-3 metal package, rated for 40 V V_CEO, 30 A I_C, and 150 W P_tot at T_c ≤ 25 °C. It is designed for linear audio amplifiers and inductive switching circuits such as relay drivers and motor controls.

For engineers reviewing the 2N3771 datasheet, 2N3771 pinout, 2N3771 application, or 2N3771 equivalent, key selection criteria include sustained voltage capability under inductive load (V_CEV(sus) = 50 V), low saturation voltage (V_CE(sat) = 2 V @ 15 A/1.5 A), and rugged second-breakdown performance (I_s/b = 6 A @ 25 V, 1 s).

Technical Context

The 2N3771 operates as a single NPN bipolar junction transistor with epitaxial base construction, optimized for high-current linear and switching operation. Its thermal resistance (R_thj-case = 1.17 °C/W) enables direct mounting to heatsinks, and its sustaining voltage ratings (V_CEV(sus), V_VCER(sus)) reflect robustness against inductive kickback.

It features DC current gain (h_FE) of 15–60 across operating points, transition frequency f_T = 0.2 MHz, and specified cut-off currents (I_CEO, I_CBO) confirming leakage control up to 150 °C junction temperature.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	40 V - Maximum collector-emitter voltage with base open; defines safe linear amplifier rail limit
I_C	30 A - Continuous collector current; supports high-power output stages without forced cooling
P_tot	150 W - Total power dissipation at case temperature ≤25 °C; requires mechanical heatsinking
V_CE(sat)	2 V @ 15 A/1.5 A - Low saturation voltage reduces conduction loss in switching applications
R_thj-case	1.17 °C/W - Junction-to-case thermal resistance; enables predictable thermal design with TO-3 mounting
I_s/b	6 A @ 25 V, 1 s - Second breakdown current rating; critical for reliability in inductive turn-off
h_FE	15–60 - DC current gain range across 10–30 A; supports stable biasing in Class AB amplifiers

Pinout & Package

Package: TO-3 metal case (JEDEC standard), with collector connected to case for direct heatsink mounting. Dimensions per datasheet: D = 8.32–8.92 mm (base width), E = 19.00–20.00 mm (case height), U = 38.50–39.30 mm (overall length).

Pin/Terminal	Circuit Role	Design Meaning
Collector (Case)	Main current sink terminal, electrically tied to metal housing	Enables low-inductance, high-current path to heatsink; requires insulating washer if heatsink is grounded
Base	Current-controlled input terminal	Drives transistor into saturation or active region; requires ≥1.5 A base drive for full 15 A conduction
Emitter	Main current source terminal	Completes high-current loop; low-impedance connection essential for stability in switching

Key Features

Feature	Design Value
High Sustaining Voltage	V_CEV(sus) = 50 V with V_EB = −1.5 V - Enables reliable operation with flyback voltages in relay/motor drives
Rugged Second Breakdown	I_s/b = 6 A @ 25 V, 1 s - Withstands transient overloads common in inductive switching
Low Thermal Resistance	R_thj-case = 1.17 °C/W - Allows >100 W continuous dissipation with moderate heatsink sizing
Controlled Leakage	I_CEO ≤ 10 mA @ 150 °C - Ensures stable bias and low standby loss in high-temp environments
Epitaxial Base Construction	Improved gain uniformity and switching consistency across production lots

Applications

Audio Power Amplifier

DC Motor Driver

Use Scenario: High-fidelity Class AB push-pull output stage delivering 50–100 W into 4 Ω or 8 Ω loads.

IC Role / Device Role / Timing Role: NPN output transistor handling peak collector current up to 30 A during transients.

Use Value: Low V_CE(sat) minimizes heat generation; high h_FE simplifies driver-stage design.

Use Scenario: H-bridge or single-ended driver controlling brushed DC motors in industrial actuators.

IC Role / Device Role / Timing Role: Main switching element turning on/off motor current up to 30 A.

Use Value: V_CEV(sus) = 50 V withstands back-EMF spikes; second-breakdown rating prevents failure during stall conditions.

Relay Driver Circuit

Linear Regulator Pass Element

Use Scenario: Driving high-current electromagnetic relays (≥20 A contact rating) in PLC output modules.

IC Role / Device Role / Timing Role: Switching transistor absorbing inductive energy from relay coil during turn-off.

Use Value: Rugged V_VCER(sus) = 45 V and fast recovery reduce need for snubbers.

Use Scenario: Series pass element in high-current linear regulators for test equipment power supplies.

IC Role / Device Role / Timing Role: Adjustable current-handling transistor dissipating up to 100 W continuously.

Use Value: Predictable R_thj-case = 1.17 °C/W enables accurate thermal margining without derating.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJ15003	V_CEO = 120 V, I_C = 20 A, P_tot = 250 W, R_thj-case = 0.6 °C/W	Higher voltage rating but lower current; better for 100 V rail systems	Choose when higher V_CEO is required and thermal budget allows larger heatsink
2N3055	V_CEO = 60 V, I_C = 15 A, P_tot = 115 W, h_FE = 20–70	Lower current and power; legacy part with wider parameter spread	Acceptable for lower-power replacements where 15 A suffices and cost sensitivity is high

Compared with MJ15003 and 2N3055, the 2N3771 offers optimal balance of 40 V/30 A rating and 150 W dissipation in TO-3, making it preferred for 24–48 V industrial switching and mid-power audio where thermal management is constrained.

Availability

2N3771 is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, relay driver circuits, and linear regulator pass elements requiring stable component supply and long-term industrial availability.

Supply support for 2N3771 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The 2N3771 belongs to ST's legacy high-power discrete transistor family, developed specifically for ruggedized linear amplification and inductive switching in industrial control and audio systems.

FAQ

Is the 2N3771 pin-compatible with the 2N3772?

No. While both share the TO-3 package and pinout (collector-case, base, emitter), the 2N3772 has higher voltage ratings (V_CEO = 60 V, V_CEV = 80 V) and lower current rating (I_C = 20 A). Substitution requires verification of voltage stress and thermal limits in the target circuit.

What is the recommended heatsink interface for the 2N3771?

A mica or silicone insulating washer with thermal grease is required between the TO-3 case and heatsink when the heatsink is grounded, due to collector-to-case connection. Mounting torque must not exceed 10 in·lb to avoid case deformation and thermal resistance increase.

Does the 2N3771 support pulse-width modulation (PWM) switching?

Yes - its 300 µs pulse rating, 2% duty cycle, and 6 A second-breakdown current support PWM operation in motor and lamp dimming applications. However, switching speed (f_T = 0.2 MHz) limits use to ≤20 kHz; gate/base drive must minimize storage time.

Can the 2N3771 be used in parallel configurations?

Yes, but only with emitter-ballasting resistors (0.1–0.22 Ω) to ensure current sharing. The device's positive temperature coefficient of V_BE aids thermal stability, but mismatched h_FE and layout asymmetry require careful PCB routing and matched base drive impedance.

2N3771 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 30 A

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

Vce Saturation (Max) @ Ib, Ic:: 4V @ 6A, 30A

Current - Collector Cutoff (Max):: 10mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 15 @ 15A, 4V

Power - Max:: 150 W

Frequency - Transition:: 200kHz

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Chassis Mount

Supplier Device Package:: TO-3

2N3771 FAQ

1.How can I place an order for 2N3771 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N3771 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 2N3771 reliable?

The price and inventory of 2N3771 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N3771 is usually 5 days.

3.What payment methods are accepted for 2N3771?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N3771 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N3771?

2N3771 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N3771 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 2N3771?

For technical support, including 2N3771 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N3771 requirements.

6.How does Aetrix verify that 2N3771 is sourced from the original manufacturer or authorized distributors?

All 2N3771 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 2N3771 meets industry standards.

7.What is the process for return or replacement of 2N3771?

All 2N3771 units undergo pre-shipment inspection (PSI). If there is an issue with 2N3771, 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 2N3771 part is unused and in its original packaging.

Return procedure for 2N3771:

1.Submit a request within 90 days.

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

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