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General Category => Digital discussion => Topic started by: FrED on March 22, 2008, 22:02:03 PM

Title: When use a PNP and when a NPN tramsistor?
Post by: FrED on March 22, 2008, 22:02:03 PM
Hallo!
I have a question that came to me when i try to design a switch using a relay and a transistor.

I know that there are PNP and NPN transistors. What is the difference they have and why do we have 2 types of transistors? And when do we have to use a NPN and when a PNP?
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: Andre on March 23, 2008, 09:21:04 AM
As long as i know here is no "WHEN".

Basically, the difference between PNP and NON is that PNP gets a + to the collector and needs 0 to the base to become conductive.
NPN gets 0 to the collector and needs + to become conductive.

This is the main difference. So, if you need to switch for example a relay and you have an output that sends 0 when you need to turn it on, then you must use a PNP transistor.

Also, is very usefull in reversing signals (like amplifiers).

There are no more differences between them as long as i know...
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: FrED on March 28, 2008, 00:11:11 AM
so it is a matter of judgment
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: kam on March 28, 2008, 00:41:57 AM
no not exactly. Some times it is mandatory some times not to use PNP or NPN
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: FrED on April 03, 2008, 23:55:13 PM
pffffff :-[
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: Supernova on April 04, 2008, 18:27:25 PM
Man, you have to understand. There is not neutral or ground or something like that in digital electronics. There is only + and - and they are handled the same

So if you have a + signal and you must use a transistor with it, you need a NPN otherwise a PNP...
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: FrED on April 11, 2008, 19:08:51 PM
I think i need to learn some more for transistors  :-\ :-\ :-\
Title: Re: When use a PNP and when a NPN tramsistor?
Post by: Supernova on April 12, 2008, 13:40:33 PM
Yep, they are very interesting...