[time-nuts] FE-5680A clock shaping (sine -> square wave)

[David]

I could analyze it on SPICE but I suspect the real world construction
parasitics will be what limits the performance.  I just sketched it
out in my notebook but I will see if I can post it somewhere.  Is
there a quick and dirty online schematic capture site?

It is not that complicated being a differential amplifier driving
complementary pair of emitter followers, a pair of voltage clamps, and
then a pair of complementary current mirrors configured as
transconductance amplifiers.

When you say symmetry limiting do you mean to prevent second harmonic
distortion like for driving a mixer?  I was thinking of this more for
driving a single ended transmission line cleanly while maximizing the
edge rates and minimizing jitter.  Duty cycle correction could be
added pretty easily.

The circuit you linked is going to have a little problem since both
the 2N5769 and the 2N5770 are NPN and the circuit requires a pair of
PNPs.  Other than that it looks perfect for driving a high level
mixer.

On Mon, 02 Jan 2012 15:52:18 +0100, ehydra <ehydra at arcor.de> wrote:

>Is it possible to sketch the circuit? I can SPICE it.
>
>Symmetry limiting is the holy grail and it is questionable if a discrete 
>design is way better than one of the chips.
>
>
>Here is another limiter circuit (by Chris Trask):
>http://ehydra.dyndns.info/NG/LTspice/Negative%20Impedance%20LO%20Driver.pdf
>
>
>- Henry
>
>
>David schrieb:
>> 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>
>> wrote:
>> 
>>> 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: