Hi, i know that transistor act like a switch but how do can control voltage like i want 5v to the input when the transistor is on? Which is better NPN or PNP?

 

You need to be more clear in your question.

 

With more information on what you want to do, we can help you find the right way to do it. It sounds like you have 5 volts at the input of the transistor? You can scale that voltage to be at the correct level to 'turn on' your transistor switch. There are a few different ways to do this, by attenuating the input signal or biasing differently, and it depends on what the application is.

 

Try an LM7805 +5V regulator to get your 5V, or a 6.1V zener diode (when it's forward biased, it should be around 5V), or as a last resort, string a bunch of forward biased 1N4001 diodes together until you get your 5V.

 

If you just want a simple voltage regulator using a transistor and Zener diode, see the attached. It's not terribly accurate, nor efficient, but good enough for many purposes.