biasing 74HC14 input to 1/2 VCC for small signals

That's what I figured. Femtofarads and total liberty in device geometries , something us board level designers can't do. But we have to mind lurkers who see this and don't realize it was for a chip design where Id is under designer control.

Sequence of events:

Close SW2 Close SW3 Open SW3 Open SW2 Close SW1 Observe "OUT" Open SW1 | Repeat

...Jim Thompson

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True, all 'AC were not created equal--mine was a preproduction sample. Several parts burned themselves up. I notified the vendor--Fairchild, I think--and the production parts seemed better.

Too late though--I'd already designed in an 'HC part instead.

It was for a single-stage x7 frequency multiplier, the first such AFAIK, and it saved the company. I see Paul Burridge talking about the fine points in sed circa 2004, so I s'pose now it's common knowledge.

But back to yours, your 'AC00 is driven continuously with a pretty large signal. It doesn't spend much time being linear, so it wouldn't get as hot.

Cheers, James Arthur

Agreed. A proper comparator is the way to go. I recall I considered to use an HC14 as a comparator but after digging up some specs from different manufacturors it appeared the hysteresis isn't well defined.

Electronic parts are like people: it is very odd to find a typical (conforming to normal) one.