difference between npn and pnp transisters?

Answer 1

in NPN transistors, the majority carriers are electrons. In PNP transistors, the majority carriers are"holes" holes are areas that lack electrons, hence they have a net positive charge.

Power supply and biasing arrangements are correspondingly different for both types. In NPN, the negative side of the power supply is grounded, while in PNP, it is the positive side that is grounded.

Answer 2

NPN

The symbol of an NPN Bipolar Junction Transistor.NPN is one of the two types of bipolar transistors, in which the letters "N" and "P" refer to the majority charge carriers inside the different regions of the transistor. Most bipolar transistors used today are NPN, because electron mobility is higher than hole mobility in semiconductors.

NPN transistors consist of a layer of P-doped semiconductor (the "base") between two N-doped layers. A small current entering the base in common-emitter mode is amplified in the collector output.

The arrow in the NPN transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode.


PNP
The other type of BJT is the PNP with the letters "P" and "N" referring to the majority charge carriers inside the different regions of the transistor. Few transistors used today are PNP, since the NPN type gives better performance in most circumstances.


The symbol of a PNP BJT.PNP transistors consist of a layer of N-doped semiconductor between two layers of P-doped material. PNP transistors are commonly operated with the collector at ground and the emitter connected to a positive voltage through an electric load. A small current entering the base prevents current from flowing between the collector and emitter.

Answer 3

For an npn transistor, current flows IN to the device at the base and collector, and OUT of the device at the emitter.

For a pnp, it's the other way around.

Answer 4

There are two types of silicon used in semiconuctors P-Type and N-type.

The N type silicon is doped with a material like arsenic so as to provide a suplus of electrons. In N type silicon the majority carriers of current are electrons and minority carriers are holes


The P-type silicon is doped so as to provide a surplus amount of positive carriers (Holes) in P-type there is a deficiency of electrons added to the silicon. So the Majority carriers are holes while the minority carriers are electrons..

A PN junction is formed by placing P-type and N-type silicon together. This single junction is a diode and is a polarity sensitive semicoductor which conducts in one direction.

The transistor is really two junctions formed by 3 alternating layers of doped silicon. The three layers form the Emitter(E), Base(B) and Collector(C). The Base is the middle layer.

The main difference between the PNP or NPN transistor type is polarity of connections to the emitter base and collector.