[time-nuts] TNS-BUF update

[Gerhard Hoffmann]

Am 19.08.2018 um 14:43 schrieb Bruce Griffiths:
> Yes, I looked at the plots and I see exactly what I described.
> 2nV/rtHz at frequencies somewhat above the reference current source output RC filter, rising to a high value at frequencies below the current source output filter pole.
> This is an inherent property of the architecture.

I really don't know how you come to that conclusion. Even the HLMP-6000 
needs more than
100 Hz to be better than the 3042 in its standard data sheet circuit, 
without extra filtering
provided, and the LED delivers only half the DC voltage, another 6 dB.

'Ordinary' LEDs from Toshiba or Osram(ex Siemens) are 20 to 30 db worse, 
and they are
quality parts, not unknown junk box parts.
Their 1/f corner is - OMG!!!11! -  the plot goes only to 1 MHz!

Postulating superior LED  performance at 1Hz from that is quite venturesome.
LEDs are good in comparison to el cheapo bandgaps and high voltage "Zeners",
but they cannot do magic.


And please don't say, it's the light. The measurements are made in a box 
in a box in a box
to handle the pV noise densities. My preamps are now at 70 pV/rtHz and 
there is a
chopper in statu nascendi at 100 pV sub- 0.1 Hz. Yes, I see the noise 
of  the 0.6 Ohm switches.

But I need a better FFT analyzer now. A working SPI driver @ 
1Mtransfers/sec for the
BeagleBoneBlack would do.

cheers, Gerhard


ps. I'm also interested in that time travel movie.