[time-nuts] FE-5680A clock shaping (sine -> square wave)
djl at montana.com
Fri Dec 30 14:47:58 EST 2011
Heck- for a really good risetime, all you need is a mercury-wetted relay
> What kind of performance would you expect in this application? Low
> jitter? 50 ohm output? TTL or better signal levels? Fast rise and
> fall times? Duty cycle correction?
> After reading your post I was thinking about how to go about it and
> ended up with an 8 transistor discrete design using a differential
> amplifier input and pair of current mirror transconductance amplifiers
> for the output. I have been looking into designing a pulse generator
> for oscilloscope calibration and have an interest in GPSDOs so maybe I
> will prototype this as well just to see what kind of performance a
> bunch of 2N3904 and 2N4401 jelly bean transistors can provide.
> On Thu, 29 Dec 2011 21:14:30 -0800, John Beale <beale at bealecorner.com>
>>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
>>better than others. The slow ones won't work at all at 10 MHz, and the
>>fast comparators (MAX999, ADCMP600, LT1116 etc.) are more expensive,
>>perhaps harder to work with. I tried a MAX9013 in SO-8 package and it
>>well for the job. You can see my schematic, circuit and scope plots at
>>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
>>using some hysteresis, but it may not be necessary.
>>Previous to those pics on the page, you also see a circuit which did
>>work so well, using a MAR-1 (broadband DC-1GHz MMIC amp). It's intended
>>a linear amp, and it does not saturate in a symmetric way even with
>>Here are a few other circuits of interest, which I did not try:
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Dr. Don Latham AJ7LL
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