The BD139 is a widely used NPN bipolar junction transistor (BJT) known for its use in low to medium-power amplification and switching applications. It is part of the BD13x series of transistors, which are designed for general-purpose use. Here are some key features and specifications of the BD139 transistor:
Polarity: NPN (Negative-Positive-Negative).
The BD139 has an N-type layer in the middle, sandwiched between P-type layers on the outside.
Maximum Collector Current (Ic): Typically around 1.5A.
This is the maximum current that can flow from the collector to the emitter when the transistor is in the on state.
Maximum Collector-Base Voltage (Vcbo): Typically around 80V.
This is the maximum voltage that can be applied between the collector and base terminals while keeping the emitter terminal open.
Maximum Collector-Emitter Voltage (Vceo): Typically around 80V.
This is the maximum voltage that can be applied between the collector and emitter terminals while the base is open.
Gain (hfe or Beta): Typically around 25 to 75.
The gain, denoted as hfe or Beta, represents the amplification capability of the transistor. It shows how much the collector current is amplified compared to the base current.
Package: The BD139 is commonly available in TO-126 or TO-126-3 packages, which are suitable for medium-power transistors.
Applications: The BD139 transistor is used in various low to medium-power amplification and switching applications, such as audio amplifiers, signal amplification, voltage amplifiers, and general-purpose electronic circuits.
Complementary Pair: The BD139 is often used in conjunction with its complementary PNP transistor, such as the BD140, to form a push-pull amplifier or switching pair for applications requiring bidirectional current flow.
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