So I have one unused OpAmp left in my circuit and I would like to use it as "latching comparator" (for lack of a better name), but I'm having hard time wrapping my head around it. Here is how I want it to behave:
Desired properties are:
- Fairly high input impedance
- Works without inputs reaching rail volatges
- Speed doesn't matter.
Closest thing that I found so far is this. But I wasn't able to figure out how can adapt it to my application.
I hope this makes some sense. I'm trying to keep it abstract(quick to read), but if more detail is needed or this turns out not to be possible - I'll add in more info.
Ok, so to be more precise of what my goal is:
I'm using LM3419 as bar-graph driver chip and I need a circuit that would latch when top graph LED turns on and stay untill bottom LED turns off. I use output of that to enable/disable some other chips.
LM3914 pulls constant current through LEDs, but I don't know what LEDs at what current I will use, hence arbitrary "high" and "low" levels. I have one free LM358 available and I wonder if I can make it work as described.
Wanted to add schematic representation here, but it doesn't let me (need more reputation). I hope it's understandable :P