This little module locks the upper and lower logic levels (also inverting logic) of a PWM signal. Long story short, I needed a PWM signal to stop at a certain minimum value, say 2v and and an upper limit of 3v. This can be done in software but I didn't want to do it in software because this circuit keeps the resolution at those smaller voltages. Adjust the upper level first( the top pot) and then the lower level( bottom pot). It even works with a darlington pair so you can use a darlington array.
