Here's a single-prop-delay version, which could be done in about 3 ns with one of the tiny-logic parts.
I probably wouldn't do this in production, because the switch thresholds of cmos schmitts aren't very tightly defined. My other circuit is more predictable.
There is likely a variant that uses slow negative feedback that would be demonstrably reliable but preserves the 1-gate delay. Haven't worked that one out, but it feels like there's something there.
John
John Larkin snipped-for-privacy@highNOTlandTHIStechnologyPART.com posted to sci.electronics.design:
You are welcome to any thoughts you want. Please remember that the "input" is coming from a reasonably fast comparator as it is.
John Larkin snipped-for-privacy@highNOTlandTHIStechnologyPART.com posted to sci.electronics.design:
I think i see where you went, that is kind of slick. Has to be a non inverting ST.
Fred Bloggs snipped-for-privacy@nospam.com posted to sci.electronics.design:
I think they made the original, i used some knock off a mere 20 years ago. It did the job and was cheap. If i was trying to make a real design today i would be looking for an AHCT equivalent.
John Larkin snipped-for-privacy@highNOTlandTHIStechnologyPART.com posted to sci.electronics.design:
Maybe, maybe not. Have you carefully analyzed all the propagation delays? What happens with a fast AHCT equivalent (is the '221 close enough?)?
John Larkin snipped-for-privacy@highNOTlandTHIStechnologyPART.com posted to sci.electronics.design:
Would not work in this case. As previously stated signal is from a comparator.
What difference would that make? The input is a logic level, and its time behavior has been defined.
Yes, there is a simple fix that allows reliable operation with real-world cmos schmitts. It's sort of obvious.
John
Best regards, Spehro Pefhany
Neato..a differentiator warping the signal into the hysteretic levels... Nope...I didn't guess that one.
One wild idea I had was to try and use a 4.5nS LT latching comparator in some fashion.. But nahhh.. (No I'm not affiliated with LT in anyway..)
D from BC
I'll give you simple, but the other descriptors are in your dreams. I will not get into the details of the inferiority of your 'design' other than to say even a chimp would know that mixing RC's into a first occurrence event detector makes no sense.
Just more of your delusional fantasies...must be the Lipitor has corrected your testosterone deficiency, how does it feel to be able to grow a mustache for the first time in your life...
[snip] [snip]
Neato! A non-repeatable "solution" ;-)
...Jim Thompson
Clearly it needs some delay. Maybe I should have used Jim's magical "Delay" black box.
I don't suppose you noticed that the RC drives the D pin of the flop. Hell, you obviously don't understand the circuit at all.
So design and post something and quit whining.
I've had one since I was 19. I was doing presentations to aerospace companies, like Lockheed and Boeing, and I just looked too young. The moustache helped a little. We got the contracts, so I suppose it did.
John
Hey, Jim is actually Fred in disguise!
John
Waveforms that only droop the part of the waveform you WANT to droop (trying to make your case) don't quite do that in the real world.
...Jim Thompson
Circuits process waveforms the way I want them to, because I design them that way.
Are you suggesting that I don't understand how RC circuits respond to waveforms? The only alternative seems to be that you don't. So you must be Fred, qed.
John
[snip]
Funny, your circuit doesn't produce waveforms exactly as you sketched them.
Put some numbers on a real circuit, post it, and then let the mob evaluate its efficacy.
Or are you chicken ?:-)
...Jim Thompson
Of course not. That's why they call it a "sketch." And since the component values aren't specified, it couldn't do anything "exactly."
So you *don't* understand it! That's interesting.
John
[snip]
Your recent responses have become of such a subterfuge level I have to conclude you're a leftist weenie. Bye!
...Jim Thompson
Well, either you see it, or you don't. I guess you don't.
John
Oh, I see it. It's just part of your leftist weenie persona to duck by claiming I don't understand.
Your circuit's Thompson Reliability/Repeatability Rating == 0
...Jim Thompson
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