First things first, this is a college assignment. I appreciate that people are not going to do my homework for me, but i am just asking for some guidance/research advice.
I have a pulse width modulation circuit that uses 2 555's with the output of the monostable 555 being an LED. The receiver/comparator is as follows-
The areas i must explain are-
- The resistor value RD before the LED.
- The F.E.T function.
- The PT function.
- The 3K9 resistor.
I will probably be ok with the PT and FET explanations, but struggle more with the reasoning of resistor values.
Can anybody recommend some online resources where i can learn the basic functions covered above?
Thanks