[throwawaygh]

I'm also confused by the confusion here... probably naive pattern matching? Reminds me of TAing undergrad courses where you could get more than half the class to confuse "positive feedback" and "negative feedback" on a midterm by just giving examples where stability = bad :)

[robotresearcher]

Grandparent gives the choices of ‘positive exponent growing against time’ or ‘negative exponent damping out against time’. Here we have a positive exponent damping (reducing) the output over time, because it’s value is less than one, resulting in a negative loop gain. The Wikipedia article linked up thread defines positive feedback as having positive loop gain, and negative feedback negative loop gain.

[a9h74j]

IIRC, generally a positive loop gain greater than one will lead to diverging behavior aka instability, whereas even a positive-sign to feedback, if loop gain is "less than one" will not. I might be brain-farting here, but I cannot be precise anyway, which IIRC gets into plotting poles in a complex plane. (Cue joke my applied math professor would tell, about why all the Polish people were asked to sit in the right-hand aisle of an aircraft.)

[a9h74j]

Self-reply: Not a derogatory reference. Just: "Poles in the left half-plane cause instability."