BD139 NPN Bipolar Power Transistor | 80V 1.5A TO-126

The BD139 is a medium-power NPN bipolar junction transistor (BJT) designed for general-purpose amplification and switching applications. With a collector-emitter voltage rating of 80V and continuous collector current up to 1.5A, the BD139 is widely used in power amplifiers, driver stages, SMPS circuits, and industrial control electronics.

Its TO-126 package provides efficient heat dissipation while maintaining compact PCB footprint, making it suitable for both through-hole prototyping and production environments.

Key Features

• Transistor Type: NPN Bipolar Junction Transistor

• Medium power handling capability

• High collector-emitter voltage rating

• Low saturation voltage

• Good current gain stability

• Suitable for linear amplification and switching

• Robust TO-126 through-hole package

• RoHS compliant

Typical Applications

• Audio power amplifiers

• Driver stages for relays and motors

• Linear voltage regulators

• Switching power supplies (SMPS)

• Industrial control circuits

• Signal amplification stages

• Power management circuits

• General-purpose transistor replacement

Electrical Characteristics

• Transistor Polarity: NPN

• Collector-Emitter Voltage (Vceo): 80 V

• Collector Current (Ic): 1.5 A

• Power Dissipation: 12.5 W

• DC Current Gain (hFE): 40 – 160

• Transition Frequency (fT): ~190 MHz

Mechanical Specifications

• Package / Case: TO-126

• Mounting Type: Through-Hole

• Number of Pins: 3

• Pin Configuration: Emitter – Collector – Base

• Cooling: Suitable for heatsink mounting