[time-nuts] sine to square wave circuits - performance data?
attila at kinali.ch
Wed Oct 4 12:56:56 EDT 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
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.
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