Powered analog output

Hi everyone. I am very new to the Arduino world, but eager to learn. I need to make a heated blanket increase in heat when fsr sensors are triggered. In other words I need to make an analog output corresponding to my analog input, but with en external power supply. So far all I can find is the MOSFET transistor, but that only allows me to have an on/off-output. Any quick fixes?

Thanks in advance.

The trick is to use FETs with PWM.

http://www.thebox.myzen.co.uk/Tutorial/PWM.html

Thanks. Looks like just what I was looking for!