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

onsemi BD3776STU

Name: BD3776STU
Brand: onsemi
SKU: BD3776STU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD3776STU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD3776STU.pdf

Description:: TRANS NPN 60V 2A TO-126-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD3776STU from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for medium-power linear amplification and switching applications, with V_CEO = 60 V, I_C = 2 A DC, P_C = 25 W at T_C = 25°C, h_FE = 63–160 at I_C = 0.15 A, and V_CE(sat) = 1 V at I_C = 1 A / I_B = 0.1 A - used in audio output stages and relay drivers.

For engineers reviewing the BD3776STU datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-126 package thermal performance, V_CEO/V_CBO voltage grading, h_FE classification band, safe operating area (SOA) limits, and complementary pairing with BD378.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with defined DC current gain (h_FE1 = 63–160 at V_CE = 2 V, I_C = 0.15 A; h_FE2 = 20 min at I_C = 1 A), low saturation voltage (V_CE(sat) = 1 V), and fast switching (t_ON = 50 ns, t_OFF = 500 ns under specified test conditions).

It features a rugged SOA curve supporting pulsed operation up to I_CP = 3 A (PW = 350 µs, duty cycle = 2%), junction temperature rating of 150°C, and thermal derating beyond T_C = 25°C per the published power derating curve.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - maximum continuous collector-emitter voltage before breakdown; defines safe DC voltage swing in amplifier or switch configurations
I_C (DC)	2 A - maximum continuous collector current; sets upper limit for steady-state load handling capability
P_C (T_C=25°C)	25 W - maximum power dissipation at case temperature 25°C; requires heatsinking above ambient for sustained operation
h_FE1	63–160 - DC current gain at low-mid current (I_C = 0.15 A); determines base drive requirements for linear biasing
V_CE(sat)	1 V - collector-emitter voltage in saturation at I_C = 1 A / I_B = 0.1 A; directly impacts conduction loss in switching use
t_OFF	500 ns - turn-off delay under V_CC = 30 V, R_L = 60 Ω, I_B1 = –I_B2 = 0.05 A; constrains maximum switching frequency in hard-switched circuits

Pinout & Package

BD3776STU is housed in a TO-126 plastic package with integral metal tab for heatsink mounting. Pin 1 is Emitter, Pin 2 is Collector (connected to tab), Pin 3 is Base - standard configuration for medium-power NPN transistors in this family.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path for majority carriers	Connected to ground or low-side reference; must handle full load current and support stable emitter degeneration
2 (Collector)	Current entry path; electrically tied to metal tab	Mounted to heatsink; requires insulated mounting hardware if tab is not at system ground potential
3 (Base)	Control terminal for minority carrier injection	Drives transistor into saturation or active region; requires current-limited drive to avoid overdrive or thermal runaway

Key Features

Feature	Design Value
Medium-power SOA	Supports pulsed I_C up to 3 A with defined safe operating boundaries across V_CE, enabling robust overload tolerance
Complementary pairing	Designed as NPN counterpart to BD378 (PNP), enabling push-pull and Class-B amplifier topologies without redesign
Thermal stability	Junction temperature rating of 150°C and documented derating curve allow reliable operation in enclosed industrial enclosures
Low V_CE(sat)	1 V saturation voltage at rated current reduces conduction losses by ~30% vs. legacy general-purpose transistors in similar packages

Applications

Audio Power Amplifier Output Stage	DC Motor Driver (Small Actuators)
Use Scenario: Final output stage in 5–15 W analog audio amplifiers driving 4–8 Ω speakers. IC Role / Device Role / Timing Role: NPN output transistor in complementary pair with BD378, delivering linear current amplification with minimal crossover distortion. Use Value: V_CEO = 60 V and h_FE = 63–160 ensure headroom for ±25 V rails and predictable bias stability across unit-to-unit variation.	Use Scenario: H-bridge half-bridge driver for 12–24 V brushed DC motors in HVAC dampers or office automation. IC Role / Device Role / Timing Role: High-current NPN switch controlling motor phase current; paired with BD378 for bidirectional control. Use Value: 25 W dissipation and SOA-rated pulse capability allow brief stall currents up to 3 A without second breakdown.
Relay/Contactor Driver	Linear Voltage Regulator Pass Element
Use Scenario: Driving 12–48 V coil relays or small contactors in PLC I/O modules. IC Role / Device Role / Timing Role: Switching element that sinks coil current when base is driven; operates in saturation for low-loss on-state. Use Value: V_CE(sat) = 1 V minimizes self-heating during continuous coil hold, extending relay lifetime and reducing PCB temperature rise.	Use Scenario: Series pass transistor in adjustable linear regulators supplying 1–2 A at ≤30 V input-to-output differential. IC Role / Device Role / Timing Role: Current-controlled pass device dissipating excess voltage as heat; biased in active region for regulation. Use Value: 150°C T_J rating and documented thermal derating enable stable operation with modest heatsinking at 1.5 A / 15 V drop.

Audio Power Amplifier Output Stage

DC Motor Driver (Small Actuators)

Use Scenario: Final output stage in 5–15 W analog audio amplifiers driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: NPN output transistor in complementary pair with BD378, delivering linear current amplification with minimal crossover distortion.

Use Value: V_CEO = 60 V and h_FE = 63–160 ensure headroom for ±25 V rails and predictable bias stability across unit-to-unit variation.

Use Scenario: H-bridge half-bridge driver for 12–24 V brushed DC motors in HVAC dampers or office automation.

IC Role / Device Role / Timing Role: High-current NPN switch controlling motor phase current; paired with BD378 for bidirectional control.

Use Value: 25 W dissipation and SOA-rated pulse capability allow brief stall currents up to 3 A without second breakdown.

Relay/Contactor Driver

Linear Voltage Regulator Pass Element

Use Scenario: Driving 12–48 V coil relays or small contactors in PLC I/O modules.

IC Role / Device Role / Timing Role: Switching element that sinks coil current when base is driven; operates in saturation for low-loss on-state.

Use Value: V_CE(sat) = 1 V minimizes self-heating during continuous coil hold, extending relay lifetime and reducing PCB temperature rise.

Use Scenario: Series pass transistor in adjustable linear regulators supplying 1–2 A at ≤30 V input-to-output differential.

IC Role / Device Role / Timing Role: Current-controlled pass device dissipating excess voltage as heat; biased in active region for regulation.

Use Value: 150°C T_J rating and documented thermal derating enable stable operation with modest heatsinking at 1.5 A / 15 V drop.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power switching and linear amplification applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD31C	V_CEO = 100 V, I_C = 3 A, P_D = 30 W, TO-220 package; higher voltage rating but larger footprint and different pinout	Preferred where >60 V rail margin or higher surge immunity is required; unsuitable for direct PCB replacement due to TO-220 vs. TO-126	Select MJD31C only when board layout allows TO-220 mounting and higher V_CEO is critical
BD139	V_CEO = 80 V, I_C = 1.5 A, P_D = 12.5 W, TO-126; lower power rating and narrower h_FE range (25–250)	Suitable for lower-current (<1.2 A) linear or switching roles where thermal budget is constrained	Choose BD139 only if load current remains below 1.2 A and thermal design cannot accommodate 25 W dissipation

Compared with BD3776STU, MJD31C offers higher voltage and power but requires mechanical redesign, while BD139 provides cost-effective substitution only in derated current and thermal conditions - neither is pin-compatible, and both demand validation of SOA and bias network stability.

Availability

BD3776STU is available at Aetrix Electronics and suitable for audio power amplifiers, relay drivers, DC motor controllers, and linear regulator designs requiring stable component supply with known thermal and switching performance.

Supply support for BD3776STU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power discrete devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.

The BD3776STU belongs to Fairchild's BD375/377/379 NPN transistor series, engineered for medium-power linear and switching applications where ruggedness, predictable gain, and thermal reliability are prioritized over ultra-high speed.

FAQ

What is the maximum continuous collector current rating for BD3776STU?

The BD3776STU has a maximum continuous collector current (I_C) rating of 2 A at case temperature T_C = 25°C. This rating decreases with rising case temperature per the published derating curve - at T_C = 100°C, the usable I_C drops to approximately 1.2 A. Exceeding this limit risks thermal runaway or secondary breakdown, especially under high V_CE conditions.

Is BD3776STU pin-compatible with BD375 or BD379?

Yes, BD3776STU shares the same TO-126 package and identical pinout (Emitter–Collector–Base) with BD375 and BD379. However, voltage ratings differ: BD375 is rated for V_CEO = 45 V, BD3776STU for 60 V, and BD379 for 80 V. Substitution requires verification that the lower-voltage BD375 meets circuit stress margins, or that the higher-voltage BD379 does not compromise h_FE or switching speed requirements.

What is the typical h_FE range for BD3776STU at I_C = 1 A?

At I_C = 1 A and V_CE = 2 V, the BD3776STU exhibits h_FE2 ≥ 20 (minimum), with typical values around 40–60 depending on unit variation and temperature. This lower-gain band reflects reduced current amplification under high-current operation and informs base drive design - e.g., 1 A collector current typically requires ≥50 mA base current for reliable saturation.

Does BD3776STU have a documented safe operating area (SOA)?

Yes, the BD3776STU datasheet includes a detailed SOA graph (Figure 4) specifying maximum allowable combinations of V_CE and I_C for DC, pulsed, and transient conditions. The SOA confirms second-breakdown immunity up to 3 A pulses (350 µs, 2% duty) at V_CE ≤ 60 V, making it suitable for inductive load switching with flyback protection.

Can BD3776STU be used as a direct replacement for BD377?

Yes, BD3776STU is functionally and mechanically identical to BD377 - both are NPN transistors in TO-126 with V_CEO = 60 V, V_CBO = 75 V, I_C = 2 A, and matching h_FE classification bands. The "6STU" suffix denotes Fairchild's internal packaging and testing variant; electrical and thermal specifications are fully aligned with BD377 per Rev. A datasheet.

BD3776STU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 2 A

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 100mA, 1A

Current - Collector Cutoff (Max):: 2µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 150mA, 2V

Power - Max:: 25 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126-3

BD3776STU FAQ

1.How can I place an order for BD3776STU through Aetrix?

Please submit a Request for Quotation (RFQ) for BD3776STU 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 BD3776STU reliable?

The price and inventory of BD3776STU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD3776STU is usually 5 days.

3.What payment methods are accepted for BD3776STU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD3776STU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD3776STU?

BD3776STU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD3776STU 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 BD3776STU?

For technical support, including BD3776STU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD3776STU requirements.

6.How does Aetrix verify that BD3776STU is sourced from the original manufacturer or authorized distributors?

All BD3776STU 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 BD3776STU meets industry standards.

7.What is the process for return or replacement of BD3776STU?

All BD3776STU units undergo pre-shipment inspection (PSI). If there is an issue with BD3776STU, 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 BD3776STU part is unused and in its original packaging.

Return procedure for BD3776STU:

1.Submit a request within 90 days.

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

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