Need help simple 0-5V to square wave 12v circuit

Hello I'm a noob here, I'm working on a Megasquirt controlled water/meth injection system for my car.

I need to convert a 0-5v Signal from my MAP sensor to a 12v square wave tachometer signal. Any links or advise on building such a circuit would be greatly appreciated.

Basically as the 0-5 voltage climbs I need the 12v square wave to climb in frequency.

Adding info: I need the output square wave to go from 15 hertz @ input .1V and 120 hertz at input 5v, Basically a linear output frequency.

Thanks in advance

Also I need the output square wave to be between 15 Hertz @ 0v and 120 Hertz @ 5v
in other words linear frequency output, thanks

Look at the first circuit here:
PWM Circuits - page 1
Adjust C as necessary for your output freq.
<als>

fsmyth said:

Look at the first circuit here:
PWM Circuits - page 1
Adjust C as necessary for your output freq.
<als>

Click to expand...

Thank you this really helps, adjusting C in the frequency equation will give me the frequency at +5v correct? thanks again

also is the output on this circuit 12v?