This is related to an earlier question of mine, but I have a different follow-up question that I wanted to make a new post for.
I'm trying to understand more about how the below circuit works, specifically the amplifier:
I've tried implementing something similar with an instrumentation amp, but was told that an opamp would be a much better choice. However, I'm not totally clear about how the opamp is functioning in this context. This doesn't appear to be set up like a difference amplifier with gain-limiting feedback resistors, and it was suggested that large gain is actually beneficial here. So here's what I don't understand:
Is this opamp configured to act as a comparator here? I.e., is the amplifier output primarily going to be saturated near 5V or ground most of the time, and avoid intermediate output voltages?
If it's acting as a comparator, what happens when the bridge is balanced? The thermistor should be held at an elevated temp when this happens, so would we essentially see a square wave at the opamp output?
If this isn't acting as a comparator, how is the gain being set?
Sorry for what might be a simple misunderstanding - I'm just having a hard time wrapping my head around the intended operation as I'm used to simpler opamp circuits.
2N2222 data sheet of sorts.