Transistors are at the heart of the electronics industry their applications are endless, they may be used in the linear region as signal amplifiers for analog applications or used in the saturation region as switches for power or digital applications. There exist several types of transistors based on their working principle, we may classify them into two main groups BJTs bipolar junction transistors and FETs field effect transistors in both cases one terminal is used to control the conductance (transconductance-varistor=transistor) between the other two terminals.