[time-nuts] FE-5680A clock shaping (sine -> square wave)
beale at bealecorner.com
Fri Dec 30 00:14:30 EST 2011
In case it's useful... there are many ways to get a square wave out from a
sine wave in, but one straightforward way is with a comparator. Some work
better than others. The slow ones won't work at all at 10 MHz, and the very
fast comparators (MAX999, ADCMP600, LT1116 etc.) are more expensive, and
perhaps harder to work with. I tried a MAX9013 in SO-8 package and it works
well for the job. You can see my schematic, circuit and scope plots at the
bottom of this page:
My circuit works best with a sine wave input amplitude above 100 mVpp.
Below that level, the duty cycle starts to become noticeably worse. I am
using some hysteresis, but it may not be necessary.
Previous to those pics on the page, you also see a circuit which did not
work so well, using a MAR-1 (broadband DC-1GHz MMIC amp). It's intended as
a linear amp, and it does not saturate in a symmetric way even with large
Here are a few other circuits of interest, which I did not try:
...and by the way, my FE-5680A shows a consistent -7E-12 per degree C
temperature sensitivity (measured at case temp 42 and 52 C). Has anyone
else measured theirs?
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