ThermalRunaway
New Member
Hi everyone,
I came across this circuit earlier today (see attachment). It's actually part of a much larger circuit, but this part in particular was causing me some confusion. It's basically a comparator, and the output is used to switch an LED on or off depending on the voltage output from the POT. In practice there is some hysteresis involved, and I'm assuming that's the reason for the feedback resistor and the diode although I am completely confused with regard to how it works. Usually you operate a comparator in open-loop mode of course, but it can be triggered by noise and is very unstable so I understand why the comparator is being designed with hysteresis in mind. How does this particular circuit work though? In effect it is being used in open loop mode because the diode stops the output from being fed back to the input. How does it create the hysteresis? Who knows!!! Maybe someone here can shed some light on it for me.
I can't guarantee the resistor values because I'm trying to remember it from earlier (I didn't bring the circuit home with me)
Any advice appreciated. It's to satisfy my own curiosity, nothing more.
Brian
I came across this circuit earlier today (see attachment). It's actually part of a much larger circuit, but this part in particular was causing me some confusion. It's basically a comparator, and the output is used to switch an LED on or off depending on the voltage output from the POT. In practice there is some hysteresis involved, and I'm assuming that's the reason for the feedback resistor and the diode although I am completely confused with regard to how it works. Usually you operate a comparator in open-loop mode of course, but it can be triggered by noise and is very unstable so I understand why the comparator is being designed with hysteresis in mind. How does this particular circuit work though? In effect it is being used in open loop mode because the diode stops the output from being fed back to the input. How does it create the hysteresis? Who knows!!! Maybe someone here can shed some light on it for me.
I can't guarantee the resistor values because I'm trying to remember it from earlier (I didn't bring the circuit home with me)
Any advice appreciated. It's to satisfy my own curiosity, nothing more.
Brian