BD675 Pinout, Equivalent, Applications, Datasheet

The BD675 NPN Darlington transistor is a high-gain, high-current power device commonly used in audio amplifier stages, motor control, and voltage regulation circuits. It provides excellent amplification with minimal input drive current, making it a popular choice among designers working on high-power and high-efficiency electronic projects. In this detailed guide, we’ll cover everything about the BD675 pinout, datasheet, key features, applications, equivalents, and its complementary PNP transistor BD676.

Introduction to BD675 NPN Transistor

The BD675 transistor belongs to the BD675–BD680 Darlington NPN series, designed for medium-to-high power amplification and switching applications. It consists of two transistors connected internally in a Darlington configuration, allowing for extremely high current gain while maintaining stable operation under load.

With a collector-emitter voltage of 45 V and collector current up to 4 A, the BD675 offers strong performance in power circuits. It features an integrated base-emitter resistor, which improves switching speed and prevents leakage currents — a vital advantage for both analog and digital circuits.

Packaged in a TO-126 case, it provides superior thermal performance and can handle power dissipation up to 40 W, making it suitable for high-current linear or switching operations.

BD675 NPN Transistor

Pinout of BD675

Understanding the BD675 Pinout Configuration

The BD675 pinout follows the standard TO-126 layout, which is identical across the BD67x transistor family. When viewed from the front (flat side facing you, leads pointing down), the pins are arranged as:

Pin Configuration of BD675 Pinout

The metal tab at the back of the TO-126 package is internally connected to the collector, so proper insulation is required when mounting to a common heatsink.

Key Features of BD675 Transistor

• High DC gain due to Darlington pair configuration
• Collector current rating up to 4 A
• Collector-emitter voltage of 45 V
• Built-in base-emitter resistor for improved reliability
• High power dissipation (40 W)
• Low base drive requirements
• Complementary to BD676 PNP transistor
• Suitable for medium-power amplifier and switching designs

BD675 Transistor Datasheet and Specifications

• Collector–Emitter Voltage (VCEO): 45 V
• Collector–Base Voltage (VCBO): 60 V
• Emitter–Base Voltage (VEBO): 5 V
• Continuous Collector Current (IC): 4 A
• Peak Collector Current (ICM): 6 A
• Power Dissipation (Ptot): 40 W at Tc = 25 °C
• DC Current Gain (hFE): 750 minimum at IC = 2 A
• Collector–Emitter Saturation Voltage (VCE(sat)): 2 V max at IC = 3 A
• Base–Emitter Saturation Voltage (VBE(sat)): 2.5 V max
• Operating Junction Temperature: 150 °C max
• Thermal Resistance Junction-to-Case: 3.1 °C/W

These parameters make the BD675 transistor datasheet ideal for use in amplifier output stages, power switching circuits, and relay or solenoid drivers where both gain and current capacity are critical.

Working Principle of BD675 NPN Transistor

The BD675 transistor operates as a Darlington pair, where two NPN transistors are internally connected to multiply current gain. When a small base current flows into the first transistor, it amplifies the signal and drives the base of the second transistor, resulting in a very large collector current.

This configuration allows the BD675 to control heavy loads using a very small base current, offering efficiency and amplification suitable for audio amplifiers, motor controllers, and power regulators.

Because of its internal base-emitter resistor, the BD675 also offers better stability by preventing false triggering during low-current conditions.

More Circuit Layouts

Typical Applications of BD675

• Audio amplifier output stages
• DC motor speed controllers
• Relay and solenoid drivers
• Voltage and current regulators
• Power inverters and switching circuits
• Light dimmers and control modules
• Industrial control systems

PNP Complementary Transistor

The BD676 transistor is the PNP complementary pair of the BD675.
Both share similar voltage and current ratings, ensuring balanced performance in push-pull amplifier or dual-supply driver circuits.

When combined, BD675 (NPN) and BD676 (PNP) deliver symmetrical amplification, allowing efficient Class B or Class AB output stages with reduced crossover distortion and high power efficiency.

Equivalent Transistors and Alternatives

Several transistors can replace the BD675 depending on the application requirements:

• BD677, BD679 — higher voltage variants in the same series
• TIP120, TIP122 — similar Darlington NPN substitutes
• MJE800, 2N6035 — medium-power NPN equivalents
• MJ10016 — for higher current applications

Always check pinout and power ratings before substitution, especially in amplifier or switching circuits.

Comparison BD675 vs BD676 Complementary Transistors

The BD675 (NPN) and BD676 (PNP) are complementary Darlington power transistors designed for paired use in audio and power control applications.

The BD675 sources current and operates on the positive half-cycle, while the BD676 sinks current during the negative half-cycle, enabling balanced and distortion-free output.

Both share identical current gain, power dissipation, and voltage ratings, making them perfect for push-pull and bridge amplifier configurations.

Frequently Asked Questions (FAQ)

What is the BD675 transistor used for?

It’s mainly used for amplifier circuits, motor drivers, power regulators, and switching applications.

What type of transistor is BD675?

The BD675 is an NPN Darlington power transistor with a built-in resistor for reliable high-gain performance.

What is the BD675 pin configuration?

Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base. The metal tab is also connected to the collector.

What is the complementary transistor for BD675?

The BD676 PNP transistor is its complementary pair.

Can I use TIP122 instead of BD675?

Yes, the TIP122 can replace BD675 in many cases, but verify pinout and ratings before use.

Conclusion

The BD675 NPN Darlington transistor is a reliable and powerful component for audio amplifier, switching, and control system applications. Its high current gain, low input drive, and integrated resistor make it a preferred option for robust and efficient designs.

Paired with the BD676 PNP transistor, it delivers balanced performance and low distortion in amplifier circuits. Overall, BD675 remains a go-to choice for electronics engineers seeking dependable performance in power-control and amplification systems.

Datasheet of BD675 NPN Transistor

Click the following Button to download the datasheet of BD675 Transistor :

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