[time-nuts] NIST isolation amplifiers

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Nov 25 19:12:53 EST 2014

An  alternative is to use a Norton style amp (or other low noise high 
linearity amp without stellar reverse isolation) to boost the signal level and 
drive a set of high isolation output stages.
A relatively simple discrete current feedback amp may suffice.
For higher reverse isolation a cascode arrangement may suffice. 
Alternatively the input amp could drive a passive splitter each output of 
which drives a high reverse isolation stage.
Even a series shunt feedback stage with a low noise bias circuit can have 
low PN. Just avoid the design error in the HP3048 option K22 where the 
bias circuit is more susceptible to power supply noise than it needs to be.

On Tuesday, November 25, 2014 11:45:47 PM Dr. David Kirkby wrote:
> On 25 Nov 2014 23:10, "Bob Camp" <kb8tq at n1k.org> wrote:
> > Hi
> > 
> > For a modern build, the PZT3904’s and PZT2222’s are a pretty good 
way to
> go with this amp.
> > For normal distribution to instruments, there’s really no need to do
> anything this complex.
> > Bob
> I am also thinking about the construction of a  distribution amplifier with
> 15 or so outputs.  One thing that came to my mind, is that there may be
> some point in  having one or two outputs where more money is spent. 
Then if
> one thinks an item might be particularly sensitive to some aspect of the
> reference,  one can use that.
> One could for example have one or two outputs which have harmonics
> suppressed 100 dB, without going to unnecessary expensive on all 
> Dave
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