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

onsemi BD679G

Name: BD679G
Brand: onsemi
SKU: BD679G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD679G

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BD679G.pdf

Description:: TRANS NPN DARL 80V 4A TO-126

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD679G from onsemi is a plastic medium-power silicon NPN Darlington transistor rated for 80 V_CEO, 4.0 A collector current, and 40 W total device dissipation at T_C = 25°C, with DC current gain (h_FE) ≥750 at I_C = 1.5 A and V_CE = 3.0 V - used as output devices in complementary general-purpose amplifier circuits.

For engineers reviewing the BD679G datasheet, pinout, applications, or equivalent options, key selection considerations include its 80 V_CEO rating, TO-225 package thermal resistance of 3.13 °C/W, V_CE(sat) ≤2.5 V at I_C = 1.5 A/I_B = 30 mA, and RoHS-compliant Pb-free construction.

Technical Context

The BD679G implements a monolithic NPN Darlington pair with integrated base-emitter resistor network enabling high DC current gain and simplified drive requirements. Its structure supports operation up to +150°C junction temperature and features complementary pairing with PNP counterparts BD678G/BD678AG.

It exhibits low saturation voltage (V_CE(sat) ≤2.5 V) under specified drive conditions and maintains stable h_FE across its rated current range, making it suitable for linear and switching applications where gain stability and thermal robustness are required.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum collector-emitter voltage before breakdown; defines safe operating voltage headroom in amplifier or switch designs.
I_C	4.0 A - Continuous collector current rating; sets maximum load-handling capability in power output stages.
P_D @ T_C = 25°C	40 W - Total device power dissipation limit at case temperature 25°C; determines heatsink sizing baseline.
h_FE	≥750 - DC current gain at I_C = 1.5 A, V_CE = 3.0 V; enables low-base-drive-current operation in driver circuits.
V_CE(sat)	≤2.5 V - Collector-emitter saturation voltage at I_C = 1.5 A, I_B = 30 mA; directly impacts conduction loss and thermal rise in switching use.
R_JC	3.13 °C/W - Junction-to-case thermal resistance; critical for calculating junction temperature rise under real-world mounting conditions.

Pinout & Package

BD679G is housed in a TO-225 package (Case 77-09, Style 1), featuring three terminals with pins 2 and 4 internally connected to the collector, pin 3 to the base, and pin 1 to the emitter. The metal tab is electrically connected to the collector.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Main current exit path; referenced to ground or low-side return in common-emitter configurations.
Pins 2 & 4	Collector	High-current input node; electrically tied together and connected to the metal tab for thermal and electrical continuity.
Pin 3	Base	Control terminal; requires ~30 mA drive current to saturate the device at 1.5 A collector load.

Key Features

Feature	Design Value
Monolithic Darlington construction	Integrates driver and output transistors on one die, eliminating external interconnects and improving reliability over discrete pairs.
High DC current gain (h_FE ≥750)	Reduces required base drive current by >10× compared to standard power transistors, easing microcontroller or logic-level interface design.
Complementary PNP pairing	Designed to match BD678G/BD678AG in voltage/current ratings and gain, enabling balanced push-pull amplifier output stages.
Pb-free and RoHS-compliant	Meets global environmental compliance requirements without derating or performance trade-offs; marked with "G" suffix.

Applications

Audio Power Amplifiers	DC Motor Drivers
Use Scenario: Output stage in Class AB audio amplifiers delivering up to 20 W into 8 Ω loads. IC Role / Device Role / Timing Role: NPN Darlington output transistor providing high-current, low-distortion signal amplification. Use Value: High h_FE ensures stable biasing and minimal crossover distortion; 80 V_CEO supports ±35 V rail operation.	Use Scenario: H-bridge half-bridge leg driving 12–24 V brushed DC motors in industrial actuators. IC Role / Device Role / Timing Role: High-current switching element controlling motor direction and speed via PWM. Use Value: Low V_CE(sat) reduces conduction loss at 2–3 A loads; TO-225 package allows direct heatsinking to chassis.
Power Supply Regulators	Relay/Solenoid Drivers
Use Scenario: Series pass element in linear regulated power supplies delivering up to 3 A at 5–24 V output. IC Role / Device Role / Timing Role: Adjustable current-controlled series regulator transistor dissipating up to 25 W continuously. Use Value: 40 W power rating and 3.13 °C/W R_JC support thermally stable regulation under full-load conditions.	Use Scenario: High-side or low-side switch for 12–48 V DC relays and solenoids in PLC I/O modules. IC Role / Device Role / Timing Role: Robust switching transistor handling inductive kickback with built-in safe operating area protection. Use Value: Secondary breakdown-limited SOA curve accommodates relay coil energy discharge without snubber components.

Audio Power Amplifiers

DC Motor Drivers

Use Scenario: Output stage in Class AB audio amplifiers delivering up to 20 W into 8 Ω loads.

IC Role / Device Role / Timing Role: NPN Darlington output transistor providing high-current, low-distortion signal amplification.

Use Value: High h_FE ensures stable biasing and minimal crossover distortion; 80 V_CEO supports ±35 V rail operation.

Use Scenario: H-bridge half-bridge leg driving 12–24 V brushed DC motors in industrial actuators.

IC Role / Device Role / Timing Role: High-current switching element controlling motor direction and speed via PWM.

Use Value: Low V_CE(sat) reduces conduction loss at 2–3 A loads; TO-225 package allows direct heatsinking to chassis.

Power Supply Regulators

Relay/Solenoid Drivers

Use Scenario: Series pass element in linear regulated power supplies delivering up to 3 A at 5–24 V output.

IC Role / Device Role / Timing Role: Adjustable current-controlled series regulator transistor dissipating up to 25 W continuously.

Use Value: 40 W power rating and 3.13 °C/W R_JC support thermally stable regulation under full-load conditions.

Use Scenario: High-side or low-side switch for 12–48 V DC relays and solenoids in PLC I/O modules.

IC Role / Device Role / Timing Role: Robust switching transistor handling inductive kickback with built-in safe operating area protection.

Use Value: Secondary breakdown-limited SOA curve accommodates relay coil energy discharge without snubber components.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJE802G	Identical V_CEO = 80 V, I_C = 4.0 A, h_FE ≥750, same TO-225 package; datasheet specifies slightly higher V_CE(sat) (2.8 V typical vs. 2.5 V max for BD679G).	Valid in identical amplifier and switching roles but may require marginally higher base drive for equivalent saturation.	Preferred where cross-manufacturer second sourcing is required; pinout and footprint identical.
BD679AG	Same V_CEO, I_C, and package; differs in h_FE test condition (I_C = 2.0 A vs. 1.5 A) and higher V_CE(sat) (2.8 V at I_C = 2.0 A/I_B = 40 mA).	Better suited for higher-current switching (>1.8 A) where gain consistency at elevated current matters more than ultra-low saturation.	Select BD679AG when operating near 2 A continuous collector current; BD679G preferred for <1.8 A with tighter V_CE(sat) control.

Compared with MJE802G and BD679AG, the BD679G offers the lowest guaranteed V_CE(sat) at mid-range current (1.5 A), making it optimal for thermally constrained linear amplifier outputs and moderate-duty switching where conduction loss must be minimized.

Availability

BD679G is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, and linear power supply regulators requiring stable component supply and long-term industrial availability.

Supply support for BD679G 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The BD679G belongs to onsemi's legacy medium-power discrete transistor family designed for cost-sensitive, high-reliability linear and switching applications in industrial controls and consumer audio equipment.

FAQ

What is the maximum collector-emitter voltage rating for BD679G?

The BD679G has a maximum collector-emitter voltage (V_CEO) rating of 80 Vdc, verified per onsemi's datasheet Rev. 16. This rating applies under specified test conditions (I_C = 50 mA, I_B = 0) and defines the absolute upper limit before avalanche breakdown occurs. Exceeding this voltage risks permanent device failure, and design margins should maintain at least 20% derating in dynamic applications.

Is BD679G pin-compatible with BD679AG?

Yes, BD679G and BD679AG share identical TO-225 package pinout (Emitter–Collector–Base at pins 1–2/4–3), same mechanical dimensions, and collector-tab connection. However, BD679AG is characterized at higher test current (I_C = 2.0 A) and exhibits higher V_CE(sat) (2.8 V vs. 2.5 V max for BD679G), so functional substitution requires verification of gain and saturation behavior in the target circuit.

Does BD679G require a heatsink in normal operation?

Yes, BD679G requires a heatsink whenever power dissipation exceeds ~5 W - calculated using its R_JC = 3.13 °C/W and maximum junction temperature of +150°C. For example, at 2 A and V_CE = 2.5 V, dissipation is 5 W; without heatsinking, case temperature would exceed safe limits. Mounting to a minimum 15 cm² aluminum heatsink is recommended for continuous 4 A operation.

What is the DC current gain (h_FE) specification for BD679G?

The BD679G guarantees h_FE ≥750 when tested at I_C = 1.5 Adc and V_CE = 3.0 Vdc, per onsemi's Electrical Characteristics table. This high gain enables direct drive from logic-level sources (e.g., 5 V microcontrollers with 30 mA base current), reducing need for pre-driver stages in amplifier or switching applications using BD679G.

Is BD679G RoHS-compliant and lead-free?

Yes, BD679G is explicitly designated as Pb-free and RoHS-compliant per onsemi's datasheet, indicated by the "G" suffix in its part number. It meets EU Directive 2011/65/EU requirements with no lead content exceeding 0.1 wt%, and its packaging uses environmentally compliant molding compounds and plating - confirmed in the "Pb-Free Strategy" section of the BD675/D datasheet.

BD679G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

Product Status:: Obsolete

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:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126

BD679G FAQ

1.How can I place an order for BD679G through Aetrix?

Please submit a Request for Quotation (RFQ) for BD679G 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 BD679G reliable?

The price and inventory of BD679G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD679G is usually 5 days.

3.What payment methods are accepted for BD679G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD679G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD679G?

BD679G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD679G 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 BD679G?

For technical support, including BD679G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD679G requirements.

6.How does Aetrix verify that BD679G is sourced from the original manufacturer or authorized distributors?

All BD679G 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 BD679G meets industry standards.

7.What is the process for return or replacement of BD679G?

All BD679G units undergo pre-shipment inspection (PSI). If there is an issue with BD679G, 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 BD679G part is unused and in its original packaging.

Return procedure for BD679G:

1.Submit a request within 90 days.

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

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