Hello friends, I hope you all are doing great. In today's tutorial, we are gonna have a look at detailed Introduction to BD139. BD139 is a Bipolar NPN transistor, it is mounted in the SOT-32 plastic package. It is designed for audio amplifier and driver utilizing complementary circuits. BD139 has a gain value of 40 to 160, which determine the amplification capacity of a transistor. It has three main pinouts which are a collector, base and emitter. It is used to control (On/Off) bigger loads that consume less than 1.5A. BD139 is used in different industrial projects such as RF amplifier and Switching Circuits. In today's post, we will have a look at its pinout, Arduino interfacing, applications, Specifications, etc. I will also share some links where I have interfaced it with other microcon ...