# Bjt active in circuit, $V_{cb}$ is ignored, why?

Bjt in active region, physical representation:

In circuit:

Why is that in circuit base connects to emitter? Shouldn't it connect to "P" area, and then collector node and emitter node connect to "P". So P should be in the middle between C and E.

No?

Where is $V_{CB}$ ?

Break the figure into parts and try to understand.

First consider Base and Emitter ; Base is P and Emitter is N type. Hence they form a diode. Seeing the voltage you can say that they are forward bias therefore there is a current flow from Base to Emitter. (Electrons flow in the opp. direction)

Now consider Base and Collector ; Base is P and Collector is N type. Hence they form a diode as well. Seeing the voltage you can say that they are REVERSE bias therefore there is a NEGLIGIBLE current flow between Base to Collector or other way round. That is why no connection between the two. But there is an interesting thing going on here; since they are reverse biased there is a strong Electric field experienced at the junction of base-collector hence the electrons from emitter entering sees that field and is immediately sucked by that field and hence those electrons reach collector this is the current flow between emitter and collector. This is how BJT work basically, there are many perspectives of the working, follow what suits you the best.

• well yeah those electrons, if we talk physically, go from emitter to collector then to base then back to emitter again, no?? Yet base doesn't seem to connect to C separately.
– Jack
Nov 13, 2017 at 21:35
• I think you answering your own question, the electrons flow from emitter to collector or base , where are any charge flowing from base to collector/ collector to base? Nov 14, 2017 at 9:05
• No, I mean, electrons kinda flow in a loop? They can't just physically go from emitter to collector and "stay" there, then they will go to base - > emitter and back to collector again... No?
– Jack
Nov 15, 2017 at 5:02
• Not really To be very precise, the electrons flow from emitter to collector (and then to supply) only; but in between in base some of the electrons recombine with the holes in p-type base this leads to base current. Nov 15, 2017 at 9:41
• Please see the edited answer to understand pictorially. and May be you can ask your queries from this figure. Nov 15, 2017 at 9:43