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

STMicroelectronics BD679

Name: BD679
Brand: STMicroelectronics
SKU: BD679
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD679

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BD679.pdf

Description:: TRANS NPN DARL 80V 4A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,244

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Product details

Overview

BD679 from STMicroelectronics is an NPN complementary power Darlington transistor in SOT-32 package, featuring 80 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 for robust switching in industrial linear amplifiers and motor drivers.

For engineers reviewing the BD679 datasheet, BD679 pinout, BD679 application, or BD679 equivalent, key selection criteria include V_CEO(sus) = 80 V, V_CE(sat) = 2.5 V @ I_C = 1.5 A / I_B = 30 mA, monolithic Darlington architecture, and planar base island process for thermal stability in high-current industrial control circuits.

Technical Context

The BD679 uses a monolithic Darlington configuration with built-in antiparallel C–E diode to suppress inductive kickback during turn-off. Its planar base island technology ensures consistent h_FE linearity and high f_T frequency performance across operating temperature ranges up to T_J = 150 °C.

It operates as a high-gain, medium-voltage switching amplifier with V_CEO(sus) = 80 V (I_C = 50 mA), V_BE ≈ 2.5 V at I_C = 1.5 A / V_CE = 3 V, and low saturation voltage enabling efficient power stage operation in discrete driver stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum safe collector-emitter voltage under open-base conditions; defines upper rail limit in linear/switching power stages.
I_C	4 A - Continuous DC collector current rating; supports sustained 3–5 A peak loads with heatsinking in industrial motor controls.
h_FE	≥750 @ I_C = 1.5 A - High DC current gain reduces required base drive current, easing interface with logic-level controllers.
V_CE(sat)	2.5 V @ I_C = 1.5 A / I_B = 30 mA - Low saturation voltage minimizes conduction loss and heat generation in switching applications.
P_TOT	40 W @ T_case = 25 °C - Total power dissipation capability determines minimum heatsink requirement for thermal management.
f_T	High - Enables stable operation at audio and low RF frequencies; suitable for PWM-driven linear amplifiers up to ~100 kHz.

Pinout & Package

SOT-32 (TO-126) plastic package with standard 3-pin vertical mounting footprint, designed for through-hole assembly and direct heatsink attachment via collector tab.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitting terminal of Darlington pair	Connected to ground or low-side return path; carries full load current with minimal voltage drop.
2 (Base)	Control input for Darlington pair	Drives internal cascaded BJT; requires ~30 mA for full saturation at 1.5 A collector load.
3 (Collector)	Output terminal and heatsink connection	Electrically and thermally connected to metal tab; must be isolated from chassis unless common-ground design.

Key Features

Feature	Design Value
Monolithic Darlington configuration	Single-die integration eliminates inter-device parameter mismatch and improves thermal coupling between driver and output transistors.
Integrated antiparallel C–E diode	Provides intrinsic flyback path for inductive loads, eliminating need for external freewheeling diode in relay/motor driver designs.
Good h_FE linearity	Ensures predictable current amplification across 100 mA–3 A range, critical for analog linear regulators and Class AB amplifier stages.
Planar base island technology	Delivers improved ruggedness and consistent parametric spread versus epitaxial base processes, especially under repetitive surge stress.

Applications

Industrial Motor Drivers

Linear Power Regulators

Use Scenario: Driving 24–48 V DC brushed motors in PLC-controlled conveyor systems with PWM switching at 1–20 kHz.

IC Role / Device Role / Timing Role: Main power switch in half-bridge or emitter-follower output stage; handles bidirectional current and inductive energy recovery.

Use Value: Integrated C–E diode enables compact, reliable flyback protection without external components; 80 V V_CEO(sus) supports 48 V bus with margin.

Use Scenario: Pass transistor in adjustable 0–30 V / 3 A bench power supply with series regulation and overcurrent foldback.

IC Role / Device Role / Timing Role: High-gain series pass element controlled by op-amp error amplifier; operates in linear region with forced-air cooling.

Use Value: h_FE ≥ 750 reduces base drive burden on control IC; 40 W P_TOT allows stable 20 W continuous dissipation with modest heatsinking.

Relay & Solenoid Drivers

Audio Output Stages

Use Scenario: High-side or low-side switching of 24 V / 2 A industrial relays and pneumatic solenoids in factory automation I/O modules.

IC Role / Device Role / Timing Role: Discrete power switch interfaced to microcontroller GPIO via base resistor network; handles inductive turn-off spikes.

Use Value: Built-in antiparallel diode clamps V_CE during de-energization, preventing controller damage and EMI without added parts.

Use Scenario: Complementary NPN/PNP pair (with BD678) in Class AB push-pull output stage for 10–20 W audio amplifiers targeting industrial test equipment.

IC Role / Device Role / Timing Role: Output transistor delivering low-distortion current into 4–8 Ω speaker loads; biased for quiescent current control.

Use Value: Linear h_FE behavior ensures symmetrical gain compression; V_CE(sat) ≤ 2.5 V preserves headroom and efficiency at full output.

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
BD679A	Higher V_CEO = 80 V (same), but rated for I_C = 2 A / I_B = 40 mA with V_CE(sat) = 2.8 V; h_FE ≥ 750 @ I_C = 2 A.	Optimized for higher base drive availability and tighter saturation specs at elevated current; suited for digitally driven, high-duty-cycle switching.	Select BD679A when base drive exceeds 30 mA and thermal margin is constrained; otherwise BD679 offers better cost/performance for 1.5 A typical loads.
TIP122	V_CEO = 100 V, I_C = 5 A, but h_FE = 1000–5000 (wider spread); no integrated C–E diode; TO-220 package.	Requires external flyback diode; higher gain variability affects closed-loop stability in precision linear apps.	Choose TIP122 only if 100 V rating is mandatory and board space allows TO-220; BD679 provides superior integration and consistency for SOT-32 footprint constraints.

Compared with BD679A, the BD679 trades slightly lower base-current tolerance and higher V_CE(sat) for tighter h_FE distribution and proven reliability in legacy industrial designs; versus TIP122, it delivers guaranteed integrated protection and smaller form factor at the expense of absolute voltage headroom.

Availability

BD679 is available at Aetrix Electronics and suitable for industrial motor drivers, linear power regulators, relay/solenoid drivers, and audio output stages requiring stable component supply with long-term manufacturing continuity.

Supply support for BD679 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 belongs to ST's complementary power Darlington transistor product line, engineered specifically for robust, high-gain switching and linear amplification in industrial control equipment where reliability and integrated protection are critical.

FAQ

Is BD679 RoHS-compliant and lead-free?

Yes. BD679 is manufactured in ST's ECOPACK® package with lead-free second-level interconnect, compliant with JEDEC Standard JESD97 and EU RoHS Directive 2011/65/EU. The inner box label indicates the lead-free category and soldering profile limits.

What is the maximum safe operating temperature for BD679?

The BD679 has a maximum junction temperature (T_J) of 150 °C and storage temperature range of –65 °C to +150 °C. For continuous operation at full 4 A I_C, case temperature must be maintained ≤ 25 °C using appropriate heatsinking per the 40 W P_TOT rating.

Does BD679 require an external flyback diode when driving inductive loads?

No. BD679 integrates an antiparallel collector-emitter diode within the monolithic Darlington structure, providing intrinsic flyback path during turn-off. This eliminates the need for an external diode in most relay, solenoid, and DC motor applications.

Can BD679 be used in parallel configurations for higher current handling?

Parallel operation is not recommended without individual emitter resistors and matched devices. Due to inherent h_FE variation and thermal runaway risk in Darlington structures, ST does not specify or guarantee balanced current sharing; discrete current-sharing networks are required for multi-device implementations.

BD679 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):: 80 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

BD679 FAQ

1.How can I place an order for BD679 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD679 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 BD679 reliable?

The price and inventory of BD679 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD679 is usually 5 days.

3.What payment methods are accepted for BD679?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD679 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD679?

BD679 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD679 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 BD679?

For technical support, including BD679 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD679 requirements.

6.How does Aetrix verify that BD679 is sourced from the original manufacturer or authorized distributors?

All BD679 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 BD679 meets industry standards.

7.What is the process for return or replacement of BD679?

All BD679 units undergo pre-shipment inspection (PSI). If there is an issue with BD679, 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 BD679 part is unused and in its original packaging.

Return procedure for BD679:

1.Submit a request within 90 days.

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

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