400 Hz PWM Adjust the % value off the 1k Pot to Alter Duty Cycle set at 50% the negative rail is set to -2 Volts so you can see the swithing threshold normally set to 0 Volts for a digital systems
If you are going build this circuit I suggest that you lower the value 500 ohm to 220 and put the 1k preset in series to adjust the frequency to 400 Hz
Also this this circuit is sensitive to supply voltage so a regulated supply will be needed
