This configuration has voltage gain but no current gain. The input signal is applied between the base and the emitter terminals while the output signal is taken between the base and the collector terminals. The common base or grounded base configuration has the BASE connection common to both the input signal and the output signal. Related Products: Darlington BJT | Digital BJT | GP BJT | RF BJT These include the Common Base, Common Emitter and Common Collector configuration. There are three possible ways to connect a bipolar transistor within an electronic circuit with one being common to both the input and output. The current directions and voltage polarities for each kind of transistor are exactly opposite each other for any given state of operation. From the image below, the functional difference between a PNP transistor and an NPN transistor is the proper biasing (polarity) of the junctions when operating. The bipolar transistors have the ability to operate within three different regions which consists of Active Region (as an amplifier), Saturation (as a switch) and Cut-off (as a switch). The three terminals are known and labeled as the Emitter (E), Base (B) and Collector (C). They are so named because they conduct by using both majority and minority carriers.

It is formed of either a thin layer of P-type semiconductor sandwiched between two N-type or a thin layer of N-type sandwiched between two P-type semiconductors. The basic construction of Bipolar Junction Transistor (BJT) comprises of two P-N junctions producing three connecting terminals with each terminal being given a name to identify it from the other two.

Download bipolar junction transistor