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Entry  Sat Jan 20 01:20:37 2018, gautam, Update, Electronics, Whitening filter D990694 whiteningBoardLimitations.pdf
    Reply  Sat Jan 20 15:57:11 2018, rana, Update, Electronics, Whitening filter D990694 
       Reply  Tue Jan 23 01:33:23 2018, gautam, Update, Electronics, Whitening filter D990694 
          Reply  Wed Jan 24 00:48:47 2018, gautam, Update, Electronics, Whitening filter D990694 
Message ID: 13572     Entry time: Wed Jan 24 00:48:47 2018     In reply to: 13568
Author: gautam 
Type: Update 
Category: Electronics 
Subject: Whitening filter D990694 

I plan to do some characterization of this problem. The plan is to use THD as a metric for whether we are having hidden saturations. Pg 9 of the LT1125 datasheet tells us what fraction of THD to expect. I will use one of the several unused DAC channels available at the LSC rack to drive a 100Hz sine wave into one of the inputs of the whitening chassis, and measure the THD up to a reasonable harmonic number (will probably be set by the ADC noise) for (i) various whitening gain settings and (ii) various input signal amplitudes.

The motivation is to attempt to quantify the problem better:

  1. How bad is it to have one or more of the OpAmps in the quad IC either saturated to its voltage rails, or max output current?
  2. Can we reproduce Hartmut's observations?
  3. Are the OpAmps already irreversibly damaged because of extended abuse?

Then we can decide what, if anything, to do about this issue.

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