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

Attila Kinali attila at kinali.ch
Wed Oct 4 16:56:56 UTC 2017

On Wed, 4 Oct 2017 12:02:35 +1300 (NZDT)
Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

> I could measure the PN of the TAPR variant of the Wenzel circuit
> as well as the PN of the comparator based circuit (with CMOS output buffer).  

BTW: one thing that has been bothering me with the TAPR variant of the
Wenzel circuit is the 100µH inductor in the tail of the diff-pair.
As it presents an impedance of approximately 6k at 10MHz it is cruical
to the working of the diff-pair (which would otherwise be just two
independent transistors). But I was unable to find a 100µH inductor
with a self-resonance frequency significantly higher than 10MHz.
Quite to the contrary, most seem to mingle around 1MHz. This poses
two questions:

1) does the TADD2 mini use a special inductor?


2) Given the 100µH inductor has an SFR somewhere in the range of 1-5MHz
and is likely to have significant core losses around and/or above 10MHz,
doesn't this limit the performance of the circuit quite significantly?

I have been thinking of replacing the inductor with a current source
(simple current mirror) and at least in the spice simulations it looks
decent. No idea of the noise performance, though.

			Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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