[time-nuts] sine to square wave circuits - performance data?

Bob kb8tq kb8tq at n1k.org
Tue Oct 3 20:59:34 EDT 2017


Things can get a bit crazy doing this:

The Collins paper pretty well shows that edge speed matters. A survey 
of comparator data sheets will also suggest the same basic thing. Up to
some point (clipping maybe) increasing the levels into a chip improves things.

Not all chips will take the same max P-P input, so you can’t go to the same point
with each of them.  Some have strange breakpoints as you drive them. 

Boosting an RF sine wave amplitude can be done with a transformer or with a 
matching network. Each has it’s advantages. Both change the source impedance.
That may (or may not) impact the way the chip works. Ultimately things like broadband
phase noise must be impacted ….

It’s tempting to say that a fixed level test will give you a first cut at the various chips. 
That may be true in some cases. I’d guess that it’s not a good idea to sort down very
far on that basis ……


> On Oct 3, 2017, at 6:38 PM, Attila Kinali <attila at kinali.ch> wrote:
> Moin,
> The last couple of days, I have been looking into sine to square
> wave converters. There are a few proposed circuits[1-4] and there
> is of course Collins' paper [5]. But I am unable to find actual
> performance data of the different circuits. Does someone have
> such data and would share it with me/us?
> 			Attila Kinali
> [1] http://www.wenzel.com/documents/waveform.html
> [2] http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html
> [3] http://www.ko4bb.com/~bruce/CLKSHPR.html
> [4] https://www.tapr.org/kits_t2-mini.html
> [5] "The Design of Low Jitter Hard Limiters", by Collins 1996
> http://ieeexplore.ieee.org/document/494304/
> -- 
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
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