开云体育

You should also note, John, that there are errors in the EDN article.

The first picture shows the opamp in non-inverting configuration - this is, of course positive feedback, and sure enough it will latch to one of the rails.

Further down in the article, variations of the circuit are re-drawn in the inverting configuration - this is the correct version.

It is a quirk of AC analyses that sometimes an unstable configuration appears to be stable, when in fact it isn't. Always check in the time domain!

I presume Bob got it right. He would never have made that mistake. I'm surprised nobody else pointed that out.