Noob question: I have a pwm signal which goes up to 5 volts. I need to make some driver which will take it as input and output 0-18 volts proportional to the signal (where 0v-0v, 2.5v-9v, 5v-18v, etc.). I have an 18v power supply, I just need the pwm signal to regulate it. I'm using it to drive power to a transformer. I have only a very vague idea of how I might do this, and would greatly appreciate help.