[time-nuts] re low noise regulators
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun Dec 16 22:19:05 UTC 2007
SAIDJACK at aol.com wrote:
> Hi Bruce,
>
> The capacitors' microphonic sensitivity may actuallyy be more of a factor
> here.
>
Are electrolytics microphonic?
Ferroelectric (X7R, Z5U,Y5V, X5R, etc but not NP0/C0G) ceramic caps are
microphonic
>
>
>> It still helps to have as low a noise as possible before using such
>> brute force filtering to get that extra few dB of noise reduction.
>>
>
> It's not just a few dB, it's -3dB at 17Hz already, and that drops at ~-20dB
> per decade. At 170Hz it could theoretically give -23dB already, or in other
> words if the noise floor was entirely due to the supply voltage noise, then
> the difference would be between say -140dBc/Hz and about -160dBc/Hz at 170Hz -
> this could be a very significant improvement.
>
> You are absolutely right, it is very difficult to get low noise <10Hz.
>
> bye,
> Said
>
Bruce
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