BD139 NPN Power Transistor

The BD139 is a medium-power NPN Bipolar Junction Transistor (BJT) designed for switching and amplification applications. It is widely used in audio amplifiers, motor drivers, relay drivers, voltage regulators, power supplies, LED drivers, and DIY electronics projects. With its 80V collector-emitter voltage rating and 1.5A collector current capability, the BD139 is a reliable choice for medium-power electronic circuits.

Features

• Full Name: BD139 NPN Power Transistor
• Medium-power NPN transistor
• High current handling capability
• Fast switching performance
• Suitable for switching and amplification
• Low collector-emitter saturation voltage
• TO-126 package for efficient heat dissipation
• Reliable and durable construction
• Easy to mount with a heat sink
• Complementary to BD140 PNP transistor

Specifications

Pin Configuration

When viewed from the front (flat side facing you, leads downward):

Note: The metal tab is internally connected to the Collector (C). Pin arrangement may vary slightly between manufacturers, so always verify the datasheet before use.

Applications / Uses

• Audio amplifier circuits
• Relay driver circuits
• DC motor drivers
• Voltage regulator circuits
• LED driver circuits
• Power supply circuits
• Arduino interface circuits
• Robotics projects
• Battery charger circuits
• DIY electronics projects

Advantages

• High current capability
• Good switching performance
• Suitable for amplifier and driver stages
• Reliable TO-126 package
• Easy heat sink mounting
• Cost-effective solution
• Widely available

Size

• Package Type: TO-126
• Body Width: Approx. 8 mm
• Body Height: Approx. 11 mm
• Overall Height (with leads): Approx. 25 mm
• Lead Pitch: 2.54 mm
• Weight: Approximately 1.5 g

Package Includes

• 1 × BD139 NPN Power Transistor

Note: For applications operating near the maximum current or power ratings, use a suitable heat sink to improve heat dissipation. The BD139 is commonly paired with the BD140 PNP transistor in complementary amplifier and push-pull output circuits.