Question

How does a PNP transistor work? And what does it do? I need few concepts regarding it. I have already studied junction diodes..

Answer 1

Hi ujjwal :)

May I help you as it belongs to my field. Electronics engineering.

Answer 2

sure

Answer 3

Of course i need help.. you must be an expert in such topics.

Answer 4

So you have studied diode

So you know transistors are two opposite diodes.

Answer 5

yeah. NPN and PNP.. Combination of N and P type semiconductor.

Answer 6

its mainly amplification device.... here's too much wid transistor buddy, r u want full explaination?

Answer 7

I just need the basic ideas.. I will be glad if in the end i am able to differentiate and calculate base and emitter current.

Answer 8

Have diagram of transistor? Or just keep it in mind.

you know we require beta i.e. current gain in order to calculate current of base, collector or emitter?

Answer 9

can you explain what beta is?

Answer 10

beta is the current. It vary from transistor to transistor. It is pre-defined on the specification sheet or you say data sheet.

\[\large I_\beta=\frac{I_C}{I_B}\]
Where,
\[I_\beta=\text{Current gain}\]\[I_C=\text{Collector current}\]\[I_B=\text{Base current}\]

This formula is same for PNP and NPN transistor.

Answer 11

Does this help you dear?

Answer 12

wait a min. I have a question.

Answer 13

Yes yes sure.

Answer 14

The value of \(\alpha\)=0.9, the change in collector current in transistor if base current changes by 2 micro Amp is:

Answer 15

Oh so you are confusing between alpha and beta. right?

Answer 16

\[\alpha = I _c{}/ I _e {}\]

Answer 17

Alpha is actually known as common base current gain
Beta is actually known as common emitter current gain

But both are current gain.
I have showed you beta above. Here is alpha
\[\large \alpha=\frac{I_C}{I_E}\]
where,
\[I_C=\text{collector current}\]\[\large I_E=\text{emitter current}\]

Answer 18

\[\beta = I _c{}/ I _b{}\]

Answer 19

Yes kr7210's equations are right.

Answer 20

\[\beta = \alpha /1-\alpha \]

Answer 21

u can get ur answer by using all three formulas

Answer 22

Is there a theoretical interpretation of those formulas? I can mug them up but i don't know the theory part. still unaware of basic ideas..

Answer 23

too difficult to explain here buddy... its take too much tym to write somthng

Answer 24

ok. anyways thanks! i will come up with specific problems soon..

Answer 25

@ujjwal still need help dear?