crutschow does that circuit need the 4050 to drive a logic level mosfet? I'm trying to keep the component count to a minimum.

No, it will drive a logic-level MOSFET directly at frequencies below 1kHz.

If you use 12V power, it will directly drive a standard MOSFET.

If you use an LM339, which has 4 comparators in a package, one package will do two PWM circuits.

 

No, it will drive a logic-level MOSFET directly at frequencies below 1kHz.

If you use 12V power, it will directly drive a standard MOSFET.

If you use an LM339, which has 4 comparators in a package, one package will do two PWM circuits.

Thanks. I'd need a pull-up resistor at the output wouldn't I? What value?

 

Thanks. I'd need a pull-up resistor at the output wouldn't I? What value?

The 3kΩ (R6) shown in the schematic is fine.