Circuit configuration of BJT

A transistor has three terminals namely emitter,base and collector terminals which are all mentioned in my previous posts.So,when a transistor is connected in a circuit it requires four terminals of which two would be input and the other two would be output terminals but a transistor has only three terminals as of which one terminal has to be common to make up for the loss.As a result of which a transistor has three types of configuration namely common base,common collector and common emitter configuration.All these configuration with respective circuit diagrams will be mentioned below.There is not much of an explanation for the circuits,you only have to remember the configuration that's all.

• Common base configuration (CB)-

Here I will only mention circuits for npn transistors because as for pnp transistors only the direction of current is different otherwise everything is same.

circuit configuaration for npn transistor

Here you can see the base terminal is taken as common terminal between input and output terminals.Input signal is applied between base and emitter terminals and output is taken from collector and base terminals.

• Common emitter configuration(CE)-

                                     

Here you will observe that the emitter acts as a common terminal between input and output terminals.Input signal is applied between base and emitter terminals and output is taken out from emitter and collector terminals.

• Common collector configuration(CC)-

Here the collector terminal acts as the common terminal between the input and output terminals.Input signal is applied between base and collector terminals where the output is taken out from emitter and collector terminals.

Remember the direction of arrow for npn transistors and likewise you will be able to draw circuits for pnp transistors in these three configuration.Feel free to ask any questions!!!Till then Happy Reading!!!