Am 27.10.2015 um 13:50 schrieb Charles Steinmetz:
Gerhard wrote:
Since the LM329 was mentioned above, I tried it also. Another surprise.
HOW CAN THEY MAKE SUCH A NOISY SUBSURFACE ZENER???
0 dB = 1nV/sqrt Hz
The datasheet for both NS and LT LM329s shows broadband noise of
<70nV/sqrtHz, with a corner at ~100Hz, rising to a touch over
100nV/sqrtHz at 10Hz. That is consistent with the LM329s I have used.
So, according to the datasheet, the 10Hz noise ought to be a touch
above 40dB on your graph and the curve should level off above 100Hz at
about 30dB -- if I have done my dBs right. Still somewhat higher than
most of the other diodes you tested, but not outlandishly so.
Your data seems to be *much* worse than this, with a 1/f noise corner
at ~10kHz (!!), rising to what appears to be about 1mV/sqrtHz (!!) at
10Hz. Is it possible you got fakes? (I know someone who
It's bad, but not that bad. 10 times the voltage is 20 dB more. So
0dB = 1nV/sqrt Hz
20 dB = 10 nV
40 dB = 100 nV
60 dB = 1uV
80 dB = 10 uV/sqrt Hz
The wideband noise at, say, 46 dB would be 200 nV/sqrt Hz versus the
claimed 75 nV typical
but the corner frequency is really bad. I bought them last year from
Digi-key, still with
National as manufacturer on the bag, not TI.
I'll test a few more next weekend.
regards, Gerhard
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