[time-nuts] time-nuts Digest, Vol 91, Issue 168

Bill Fuqua wlfuqu00 at uky.edu
Tue Feb 28 23:06:34 UTC 2012

At what frequency do you have 1 nv per square root Hz with opamp and
what opamp ?
    The 1/f region is the  killer and if it is a low frequency shift in the 
effectively changing the threshold then you have to be concerned about the
1/f region.
   Discrete embedded JFETs have the best 1/f  of all such as the IF3601.
Go to www.interfet.com
Bill wa4lav

At 05:11 PM 2/28/2012 -0500, time-nuts-request at febo.com wrote:
>Date: Tue, 28 Feb 2012 11:51:54 -0800
>From: gary <lists at lazygranch.com>
>To: Discussion of precise time and frequency measurement
>         <time-nuts at febo.com>
>Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...?
>Message-ID: <4F4D305A.5030906 at lazygranch.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>You need to look at the driving impedance before you declare one
>technology "quieter" than another. That is, you have voltage noise and
>current noise. For low driving impedance, bipolar will be quieter since
>current noise will not be significant, plus a bipolar will have lower
>thermal noise. For high impedance, JFET may be a better solution.
>Opamps are around 1nv/rootHz these days. That isn't all that easy to
>achieve discretely.

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