What is the differnence between pnp and npn transistor?

Answer 1

n is electrons, p is holes

An npn transistor is a hole region sandwiched by two electron rich regions. pnp is the opposite.

has nothing to do with polarities...

see here for more details...

http://en.wikipedia.org/wiki/PNP_%28transistor_polarity%29#NPN

Answer 2

An NPN transistor needs a positive base-to-emitter voltage to turn the transistor on and conduct current from collector to emitter. A PNP transistor needs a negative base-to-emitter voltage to turn the transistor on and conduct current from emitter to collector.
In applications, NPN's are better low-side drivers for loads, and PNP's are better high-side drivers.

Answer 3

The difference is in the kind of doping that is used for the emitter, base, and collector regions of the device.

Also the polarities applied by the external circuit are reversed for pnp and npn devices.

HTH ☺

Doug

Answer 4

As you know, transistors are made of semiconductors. There are two types of semiconductors, the p-substrate and n-substrate. A p-substrate is a semiconductor(say silicon) which is doped with p type materials(Also known as type VI materials, like Phosphorous). Whereas an n-substrate is a semiconductor which is doped with n type materials (also known as type III materials).

A pnp transistor is a transistor made of two p-substrate and a n-substrate sandwiched in the middle. An npn transistor is a transistor made of two n-substrate and a p-substrate sandwiched in the middle.

Answer 5

pnp is a positive negative positive transistor
npn is a negative positive negative transistor
these are also used in amplyfier,rectifier circuits
emitter,collector,base