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
input
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
73
Bill wa4lav
At 05:11 PM 2/28/2012 -0500, [email protected] wrote:
Date: Tue, 28 Feb 2012 11:51:54 -0800
From: gary <[email protected]>
To: Discussion of precise time and frequency measurement
<[email protected]>
Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...?
Message-ID: <[email protected]>
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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