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Show us your square wave

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tggzzz:

--- Quote from: PartialDischarge on November 08, 2022, 03:58:24 pm ---Somewhere in a thread user ttggzz suggested the use of LVC gates in parallel, I made a board to test the idea and I'm getting less than 500ps rise and fall times with very nice shape, tested with a 1GHz scope:









--- End quote ---

Here perhaps: https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg1902941/#msg1902941


Good to see the results can be replicated. It looks like the scopes I was using (not mine, very fast test) used the 20%-80% times, which would be faster than the 10%-90% times.

I used 143ohms in series since the gate output is ~7ohms. I don't think that would make too much difference in practice - decoupling would make more difference.

PartialDischarge:
I tried with a 74VHC gate but it is slower, I'm very happy with the results since 2.5V 500ps is very useful for many applications, it is a fairly cheap solution and aberrations are minimal which I consider important

tggzzz:

--- Quote from: PartialDischarge on November 08, 2022, 05:41:38 pm ---I tried with a 74VHC gate but it is slower, I'm very happy with the results since 2.5V 500ps is very useful for many applications, it is a fairly cheap solution and aberrations are minimal which I consider important

--- End quote ---

Agreed.

You can also reduce the output swing by reducing the PSU voltage, but the transition time increases. Try reducing Vcc  to 1V or so, and seeing if you get a 0.5V swing with 3ns risetime (and some "pre-undershoot" for want of a better term). You can go even lower, with some entertaining[1] aberrations :) The aberrations are gone by 1.7V or so, as expected.

[1] I'm easily entertained :)

tchiwam:
4 outputs on top of each other ;)

100us pulse 1 PPS rising edge ~3GHz BW

tggzzz:

--- Quote from: tchiwam on January 07, 2023, 08:33:51 pm ---4 outputs on top of each other ;)

100us pulse 1 PPS rising edge ~3GHz BW

--- End quote ---

4 outputs of what?

Why not use averaging?

PPS? And those figures don't seem to match the figures in the photograph.

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