[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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