+12 Generation from PIC
The PWM output available from many PIC chips can be used to generate 12 volts. This is very useful in making programmers for PICs that run on +5 volts only.
This is a basic voltage multiplier circuit. RB3 puts out 100 khz by setting up the proper registers in the PIC. The result is about 12 volts (or so) at C6/R8.
In this circuit, D7 provides 5 volts when the PWM signal is turned off.