adjustable frequency PWM controller with output amplifier, built and tested and it works well.
to build:
- U1 is LM393 dual low power comparator;
- connect the 1k pullup resistor to the output of U1-1;
- don't install 101pf cap, it's just there to shut EC up;
- change the 102pf cap on U1-2 + input to 10nF, or higher for lower frequencies.
- all resistors 2%;
- output transistors are pn100/200;
- 681pF cap defines the bandwidth. pick higher values for lower frequencies, etc.
