sine to square wave circuits - performance data?
On Wed, 4 Oct 2017 12:02:35 +1300 (NZDT)
Bruce Griffiths bruce.griffiths@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:
- does the TADD2 mini use a special inductor?
and
- 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
The inductor in the T2-Mini is nothing special.
On Oct 4, 2017, 12:57 PM, at 12:57 PM, Attila Kinali attila@kinali.ch wrote:
On Wed, 4 Oct 2017 12:02:35 +1300 (NZDT)
Bruce Griffiths bruce.griffiths@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:
- does the TADD2 mini use a special inductor?
and
- 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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Hoi Attila
I've unearthed the TAPR T2-mini.
I need to obtain an 8 pin DIP header so that I can connect pins 2 +3 on the PCB DIP socket.
Then I can test PN etc as function of input signal level at 10MHz.
May take a week or so to arrive.
Meanwhile I have an optical interferometer to work on.
Bruce
On 04 October 2017 at 20:23 Attila Kinali attila@kinali.ch wrote:
Hoi Bruce,
Thanks for the link. That's some nice data.
On Wed, 4 Oct 2017 12:02:35 +1300 (NZDT)
Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:
I have measured the PN of the LTC6957-4 at 10MHz.
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).
This would be very helpful. I have wondered how the modified Wenzel
circuit compared to an LTC6957 or a simple comparator.
Attila Kinali
--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering. -- The Doctor