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

STMicroelectronics BD677

Name: BD677
Brand: STMicroelectronics
SKU: BD677
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD677

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BD677.pdf

Description:: TRANS NPN DARL 60V 4A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:3,622

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Product details

Overview

BD677 from STMicroelectronics is an NPN complementary power Darlington transistor in SOT-32 package, featuring 60 V V_CEO, 4 A I_C, 40 W P_TOT, h_FE ≥ 750 at I_C = 1.5 A, and integrated antiparallel collector-emitter diode-used in industrial linear amplifiers and switching regulators.

For engineers reviewing the BD677 datasheet, BD677 pinout, BD677 application, or BD677 equivalent, key selection criteria include V_CEO rating, DC current gain linearity, saturation voltage under 2.5 V at 1.5 A, thermal dissipation capability, and monolithic Darlington topology with built-in diode for inductive load handling.

Technical Context

The BD677 employs planar base island technology to achieve high f_T and good h_FE linearity across operating current range. Its monolithic Darlington configuration integrates a base resistor network (R1 ≈ 15 kΩ, R2 ≈ 100 Ω) and an antiparallel C–E diode for flyback energy clamping.

This device operates as a high-gain, medium-voltage power switch with sustained V_CEO(sus) of 60 V at I_C = 50 mA and T_J up to 150 °C-designed for robustness in non-isolated industrial power stages where base drive efficiency and thermal stability are critical.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - maximum safe collector-emitter voltage with open base, defining upper limit for linear/switching operation in 48 V industrial rails.
I_C	4 A continuous - steady-state current-handling capacity enabling use in 20–30 W output stages without forced cooling.
h_FE	≥ 750 at I_C = 1.5 A - high DC gain reduces required base drive current, easing control circuit design in discrete amplifier or regulator feedback loops.
V_CE(sat)	2.5 V max at I_C = 1.5 A, I_B = 30 mA - low saturation voltage minimizes conduction loss and self-heating during on-state operation.
P_TOT	40 W at T_case = 25 °C - total power dissipation rating sets thermal derating curve for heatsink sizing in enclosed enclosures.
T_J(max)	150 °C - maximum junction temperature allows reliable operation in ambient up to 85 °C with appropriate thermal interface design.

Pinout & Package

SOT-32 (TO-126) three-terminal plastic package with standard pin assignment: Pin 1 = Base, Pin 2 = Collector (tab-connected), Pin 3 = Emitter. The metal tab is electrically connected to the collector and serves as primary thermal path.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Base	Control input with internal 15 kΩ series resistor-accepts TTL-compatible drive and simplifies external bias network.
Pin 2	Collector	Main power terminal, internally bonded to metal tab-requires insulated mounting when chassis-grounded.
Pin 3	Emitter	Power return node; internal antiparallel diode cathode connects here-enables freewheeling in inductive switching.

Key Features

Feature	Design Value
Monolithic Darlington + diode	Single-die integration eliminates discrete diode placement error and improves switching timing consistency in motor drives.
High h_FE linearity	Gain remains stable over I_C = 0.1–3 A range-reduces distortion in Class AB audio or precision current-source applications.
Planar base island process	Enables tighter parameter distribution and improved f_T vs. older epitaxial processes-supports faster turn-on in PWM circuits.
ECOPACK® lead-free packaging	RoHS-compliant construction with JEDEC JESD97 marking-meets industrial environmental compliance without solderability trade-offs.

Applications

Industrial Linear Amplifier

DC Motor Driver Stage

Use Scenario: High-fidelity 20 W audio output stage in programmable logic controller (PLC) I/O modules.

IC Role / Device Role / Timing Role: NPN power output transistor delivering low-distortion analog current into 4–8 Ω loads with minimal base drive overhead.

Use Value: h_FE ≥ 750 ensures <1 mA base current suffices for full 3 A peak swing-reducing driver IC loading and PCB space.

Use Scenario: H-bridge low-side switch in 24 V brushed DC motor control for factory automation actuators.

IC Role / Device Role / Timing Role: Power switching element handling 3 A continuous current with integrated flyback diode for inductive kick suppression.

Use Value: Built-in antiparallel C–E diode eliminates need for external 1N540x, reducing BOM count and layout complexity.

Switching Regulator Pass Element

Relay Driver Interface

Use Scenario: Series pass transistor in adjustable 0–30 V, 2 A bench power supply with analog voltage control loop.

IC Role / Device Role / Timing Role: Linear-mode power transistor dissipating up to 35 W during regulation-leveraging 40 W P_TOT and 150 °C T_J(max).

Use Value: V_CEO = 60 V provides 30 V headroom above 30 V output, ensuring safe operation during transient overvoltage events.

Use Scenario: Direct-drive interface between microcontroller GPIO and 24 V industrial relay coil (80 mA, 300 mH).

IC Role / Device Role / Timing Role: Single-transistor relay driver with internal base resistor network eliminating external R_B and simplifying firmware-level on/off control.

Use Value: Integrated R1 = 15 kΩ enables direct 3.3 V/5 V MCU output connection-no level-shifting or pull-up resistors required.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TIP122	V_CEO = 100 V, h_FE = 1000 min, no integrated diode, TO-220 package	Higher voltage margin but requires external flyback diode and larger footprint	Preferred when >60 V rail or higher gain is needed; not drop-in due to missing diode and different pinout
BD679	V_CEO = 80 V, same SOT-32 package, identical pinout and internal diode	Direct upgrade path for designs needing extended voltage headroom without layout change	Select when system rail exceeds 48 V or transient immunity must cover 80 V spikes

Compared with TIP122 and BD679, BD677 offers optimal balance of voltage rating, thermal performance in compact SOT-32, and integrated protection-making it ideal for cost-sensitive 24–48 V industrial controls where board space and BOM count are constrained.

Availability

BD677 is available at Aetrix Electronics and suitable for industrial linear amplifiers, DC motor drivers, switching regulator pass elements, and relay driver interfaces requiring stable component supply and long-term manufacturability.

Supply support for BD677 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, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for industrial, automotive, and consumer markets.

The BD6xxx series targets industrial power control applications, delivering rugged, high-gain Darlington transistors optimized for reliability in harsh environments and ease of use in discrete power stage design.

FAQ

What is the maximum safe continuous collector current for BD677 at 70°C case temperature?

At T_case = 70 °C, BD677's maximum continuous collector current is derated to approximately 2.8 A. This is calculated using its 40 W P_TOT rating and thermal resistance (R_θJC ≈ 0.625 °C/W per datasheet), yielding ~28 °C allowable rise above 70 °C before reaching 150 °C T_J. Derating curves in Section 3 confirm this value.

Does BD677 require an external flyback diode when driving inductive loads?

No. BD677 integrates a monolithic antiparallel collector-emitter diode, explicitly designed for flyback energy recirculation in relay, solenoid, and motor applications. This eliminates the need for external diodes like 1N4007 or BY228 in most standard inductive switching configurations.

Can BD677 be used in parallel with another BD677 for higher current handling?

Parallel operation is not recommended without individual emitter resistors. Due to h_FE variation and thermal coupling, current sharing is unstable. The datasheet does not specify matching or paralleling guidelines, and thermal runaway risk increases significantly above 2.5 A per device without active balancing.

Is BD677 suitable for Class D audio amplifier output stages?

No. BD677 is optimized for linear and quasi-linear switching (e.g., PWM at ≤20 kHz), not high-frequency Class D operation. Its f_T is unspecified in absolute terms, and switching times (t_on/t_off ≈ 1–2 µs) are too slow for efficient >200 kHz switching. Use dedicated MOSFETs or gate drivers instead.

BD677 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 4 A

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

Vce Saturation (Max) @ Ib, Ic:: 2.5V @ 30mA, 1.5A

Current - Collector Cutoff (Max):: 500µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 750 @ 1.5A, 3V

Power - Max:: 40 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32-3

BD677 FAQ

1.How can I place an order for BD677 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD677 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 BD677 reliable?

The price and inventory of BD677 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD677 is usually 5 days.

3.What payment methods are accepted for BD677?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD677 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD677?

BD677 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD677 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 BD677?

For technical support, including BD677 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD677 requirements.

6.How does Aetrix verify that BD677 is sourced from the original manufacturer or authorized distributors?

All BD677 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 BD677 meets industry standards.

7.What is the process for return or replacement of BD677?

All BD677 units undergo pre-shipment inspection (PSI). If there is an issue with BD677, 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 BD677 part is unused and in its original packaging.

Return procedure for BD677:

1.Submit a request within 90 days.

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

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