[time-nuts] FE-5680A clock shaping (sine -> square wave)
davidwhess at gmail.com
Tue Jan 3 19:59:30 UTC 2012
On Tue, 03 Jan 2012 07:01:13 +0100, ehydra <ehydra at arcor.de> wrote:
>> 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?
>Scan it. I will make a LTspice file.
>> 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.
>I want to SEE it including all circuit parameters. Thank you.
I am entering it into LT Spice for practice. I will post the results
and files here when done. I need to rethink the level shift
>> 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.
>Hm. I think second harmonic distortion looks very much like intentional
>symmetric waveform in the first instance. The fun begins if we decide to
>look for equal time distance or equal power for both phases. Interesting.
>> 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
>As far as I know driving a mixer was the circuit intention. I SPICEd it
>with BFR93 types. The circuit has a high reflection coefficient,
>unfortunately. Maybe this is unavoidable and we need a diplexer.
The output is low impedance, unmatched, and I suspect not quite
symmetrical so I would expect this. Does it matter though if the
mixer is close by?
>Yes, looks like an typo for having 4 NPNs there. I will clarify this
>with Chris Trask. Thanks.
Unfortunately, RF PNP transistors tend to be rare or expensive so when
I saw that schematic my first thought was, "Hmm. I wonder if that is
the RF PNP I have been looking for. I did not know the 2N5770 had a
PNP complement. Wait a sec . . ."
I have been considering the PNP BFG21 and NPN BFG97 made by NXP. They
are SOT-223 so should be easier to prototype with than a smaller
The On Semiconductor TO-92 NPN MPSH10 and PNP MPSH81 would be good
also but the later is being discontinued.
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