I have a colleague who is off work for the next 2 weeks and has asked me to finish off one of his schematic designs. I have a list of operations it needs to be able to perform, seems simple enough.
I got round to making a start on it today, and after having a browse through what he has already done, I notice something that I haven't seen before.
Here is the basics of what it looks like:
I have not seen an op amp circuit which uses a diode in the feedback circuit in this way. I recognise it is a window comparator, and this part of the circuit is used to detect a voltage level and turn on an LED if it goes above or below a threshold. I just can't work out what the point of the resistor and diode is in the feedback.
My go-to op amp configuration PDF is one from texas instruments (LINK) and I couldn't find one like this. So can anyone tell me what the function is of this feedback circuit?
NOTE: I have labelled things as V1, V2, OUT etc as they should be irrelevant to the circuit, V1 and V2 are measuring the input voltage, Vref is the threshold, and the output toggles LEDs
EDIT: I have updated the schematic to include the resistors that Andy aka mentioned, the values of resistance are what was on the schematic at the time, they may be incorrect, I am unsure, as the schematic is not finished.