Re: First look at GlueX Preamp response with FDC

[Mitch Newcomer <mitch@hep.upenn.edu>]

Great Simon.   Two comments.
1) Can you simply turn down  the HV  to eliminate the clipping?
2) The polarity of the signals at the output of the preamp will not 
change  for Anode or Cathode input due to the use of a dual input preamp.
    Negative (Anode ) signals  go to Input A  and Positive (Cathod) 
signals go to Input B.    ( I would say the +  and - inputs but in a non 
fed back
differential output system the  + and - concept are nearly arbitratry.  
We use the A, and B convention because the shaper has a  pre offset to 
exploit more of the available  dynamic range.      - Mitch

Simon Taylor wrote:
> Hello, everyone.
>
> Fernando and I looked at real signals from the FDC prototype using the
> GlueX preamp boards this afternoon.  The pulses were generally quite large
> to the point of possibly saturating the output of the shaper board I am
> using to look at the signals.  The noise level was low.
> I have put some photographs of scope traces on the web in the FDC logbook
> at
> http://www.jlab.org/htbin/PHYSICS/halld/enote112.pl?nb=notebook&action=view&page=348
>
> Simon
>