Ardunio output voltage

Guys , i need to increase my arduino max output voltage from 5v to 12v and the rise should be linear say from 0,0.1,0.2v and so on . please guide me through the things to be done :(

How much current do you need to output (to what?) and which voltage are you powering your Arduino with?
Depending on the answers, the way to do it may go from simple to more complex.

i need to increase my arduino max output voltage from 5v to 12v

Do you mean from the digital pins? There is no easy way.

The simplest way would be to add a D/A converter and then amplify the output. How many pins do you want to increase like this? It could prove expensive. Why do you want to do this? There might be a way round the requirement.