I dont know much about electronics.While studying about transistors,i had a doubt about the middle layer.If the emitter and middle layer becomes forward biased, and collector and middle layer becomes reverse biased,how does middle layer have both the charge in order to get reverse and forward biased at the same time?Pardon me if i understood it the wrong way.

 

It's not the layers that are biassed, it's the junctions between them.
If base voltage is greater than emitter voltage, the base-emitter junction is forward biassed. If collector voltage is greater than base voltage then the base-collector junction is reverse biassed.

 

Hello there,welcome to AAC!
I need to see exactly what you are seeing or studying can you post a link a picture or just draw it on a piece of paper.

 

Hello there,welcome to AAC!
I need to see exactly what you are seeing or studying can you post a link a picture or just draw it on a piece of paper.

From this video.....

 

Welcome to AAC!

If the emitter and middle layer becomes forward biased, and collector and middle layer becomes reverse biased,how does middle layer have both the charge in order to get reverse and forward biased at the same time?

A picture would be helpful. Your use of charge is confusing.

A bipolar junction transistor has two junctions. In active mode, the BE junction is forward biased and the CB is reverse biased.

 

It is the battery or voltage sources that create the potential differences across the junctions. The base is more positive than the emitter, so that junction is forward biased. The collector is similarly more positive than the base, so the base collector junction is reverse biased.

\( V_b>V_e\implies V_{be}>0\implies \text{Forward Biased} \)

\( V_b < V_{c}\implies V_{bc}<0\implies \text{Reverse Biased} \)

 

So,in a PN junction diode, the junction is biased and not the diode as whole ,right?

 

So,in a PN junction diode, the junction is biased and not the diode as whole ,right?

What happens at a pn-junction is a bit more complicated than a simple model can convey. The simple explanation is that the external potential (aka voltage) changes the impediments to current flow in such a way that a semi-conductor becomes an actual conductor.

 

So,in a PN junction diode, the junction is biased and not the diode as whole ,right?

Trying to model a transistor as diodes will only lead to more confusion.

This diagram is from an ECE322 course at CMU: