BD139 transistor

BD139 Transistor Datasheet pinout

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  • Bipolar (BJT) Single Transistor, NPN, 80V, 1.5A, 12.5W, TO-126, Through Hole

BD139 is the medium power NPN bipolar junction transistor. The BD139 is a commonly used NPN power transistor designed for audio, switching, and amplifier applications. It has max output current load capacity across collector to emitter upto 1.5A

Specifications of BD139

  • Type: NPN
  • Maximum Collector-Emitter Voltage (Vceo): 80V
  • Maximum Collector-Base Voltage (Vcbo): 100V
  • Maximum Emitter-Base Voltage (Vebo): 5V
  • Maximum Collector Current (Ic): 1.5A
  • Maximum Power Dissipation (Ptot): 12.5W
  • DC Current Gain (hFE): 25 to 250 (depending on the operating current)
  • Package: TO-126

Collector -Emitter Voltage VCEO

BD135: 45V

BD137: 60V

BD139: 80V

Collector Current IC : 1.5A

Collector Peak Current ICM : 2.0 A

Features of BD139 transistor

  1. High Voltage Capability: Can handle up to 80V between the collector and emitter.
  2. Moderate Current Handling: Can switch or amplify currents up to 1.5A.
  3. Low Saturation Voltage: Ensures efficient operation with low power loss.
  4. Thermal Stability: The package allows for better heat dissipation compared to smaller transistors.
  5. High Gain: Suitable for various amplification tasks due to its high DC current gain.

BD139 transistorUses of the BD139 Transistor

  1. Audio Amplifiers:
    • Used in the output stages of audio power amplifiers where moderate power and good linearity are required.
  1. Switching Applications:
    • Commonly used in circuits for switching loads, such as motors, relays, and LEDs, due to its ability to handle relatively high currents and voltages.
  1. Voltage Regulators:
    • Plays a role in maintaining a stable voltage in power supply circuits, often used in conjunction with other components.
  1. Driver Stages:
    • Utilized in driving higher power transistors in larger circuits, serving as an intermediary stage to boost current capacity.
  1. General-Purpose Applications:
    • Suitable for a wide range of electronic circuits, including signal amplification, oscillators, and other medium-power applications.

Pin Configuration:

  1. Collector (C): Connected to the load or the positive voltage supply in a typical circuit.
  2. Base (B): The control terminal, which modulates the flow of current between the collector and emitter.
  3. Emitter (E): Typically connected to the ground or the negative supply voltage.

Practical Tips for Using the BD139

  • Heat Management: Use a proper heatsink if operating near the maximum power dissipation to prevent thermal damage.
  • Base Resistor: Use a base resistor to limit the base current and protect the transistor from excessive current.
  • Circuit Design: Check the hFE range to ensure the transistor matches the required gain for your circuit.

The BD139 is a versatile transistor widely used in electronics due to its robustness and reliable performance across a range of applications.

Complementary BD136, BD138, BD140 (PNP) are recommended with BD135, BD137, BD139

Equivalent – BD230(ECB), BD233(ECB), TIP31C(BCE) etc

bd139 footprint dimension size

Download Datasheet Pdf


bd135_bd137_bd139 datasheet (CDIL




BD139-Datasheer (ON Semiconductor


bd135_bd137_bd139 (Motorola)




BD135 -BD139 datasheet (Philips)



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