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BD139 transistor is a popular NPN type used in a variety of electronic circuits. It is an ideal transistor due to its high collector current and low cost. Due to these features, it is used in educational electronics projects as well as in commercial electronics circuits. This transistor can load up to 1.5A so you can drive high-current components like high-current relays, motors, LEDs, etc. It can easily survive in almost all electronic circuits because the collector-emitter and collector base voltage is very high up to 80 volts. It is also ideal to use in amplifier circuits due to 12.5W collector dissipation. The saturation voltages of BD139 are just 0.5V.
| NO | Pin Name | Description |
| 1 | Emitter | Current Drains out through the emitter |
| 2 | Collector | Current flows in through the collector |
| 3 | Base | Controls the biasing of the transistor, Used to turn ON & OFF. |
BD136, BD138,BD230, 2SC5171S, BD349, and BD379
D882 is the perfect alternative to BC139
Complementary of BD139 is BD140
This transistor was first manufactured by Philips rated at 160MHz especially for audio applications, later it was cloned by other manufacturers like ST, Samsung, etc.
Due to a high collector current of 1.5A, this transistor can be used to control (On/Off) high loads that consume less than 1.5A. The saturation voltages (Base Emitter Voltage VBE) of only 5V, which makes it easy to use in digital electronics which has an operating voltage of 5V. It comes in a plastic jacket which is the way its cost is very less and the most important feature of a plastic jacket is that it will not be effect by other noise.
The datasheet of this transistor is given in this link.
BC547, BC548, BC549, 2N2222A, C945, C1815