Might only detect the +0.2V positive swing, this make it much easier right?

But on the input to the comparator how do you accurately put 0.2v on one of the =
inputs, also do comparators already have some imbalance on the inputs and how =
do you compensate?

R.

 >>  Two op amps or two comparators. What you're looking for is called a window
 >>  comparator. The hardest part will be level shifting the signal into the 0
 >>  to 5V range without actually affecting the signal over the whole frequency
 >>  range. You may have to look into generating a negative voltage supply.
 >>  --
 >>  Greg

 >>  Rick C. wrote:
 >>  >I'll poke around and see if can a schematic. The one I have in mind uses
 >>  >two opamps.
 >>  >Rick
 >>  >
 >>  >Richard Sloan wrote:
 >>  >
 >>  > >  >>  A couple more things need to be known before anyone can really
 >>  > give you an
 >>  > >  >>  answer.
 >>  > >  >>  1) Are we assuming p-p freq. to be within audio range?
 >>  > >
 >>  > > any freq, we are dealing with audio range freq however, so it should
 >>  > work for 20-15k range
 >>  > >
 >>  > >  >>  2) How long does the LED have to sustain after receiving
 >>  threshold?
 >>  > >
 >>  > > well could just blink for the instant it happens, might be nice to
 >>  have
 >>  > it stay on for 0.25 - 0.5s
 >>  > >
 >>  > >  >>  3) Are you planning to use a PIC to do the detecting? (overkill
 >>  > really)
 >>  > >
 >>  > > no opamp / comparator
 >>  > >
 >>  > >  >>  4) Do you want to detect on > +.2 and/or -.2v?
 >>  > >
 >>  > > yes
 >>  > >
 >>  > >  >>  5) We need to know if you are wanting to mix analog with digital
 >>  to
 >>  > >  >>  achieve your goal, or straight analog citcuitry.
 >>  > >
 >>  > > hopefully its just analog
 >>  > >
 >>  > >  >>  There are many sample circuits in the National Linear Databooks
 >>  and
 >>  > >  >>  application notes that will probably provide what you want. A
 >>  simple
 >>  > >  >>  opamp will achieve your
 >>  > >  >>  desired results. A Norton Amp such as the LM3900 will probably
 >>  > work and
 >>  > >  >>  will operate from 4v to 36v single ended supply. You'll have to
 >>  dig
 >>  > >  >>  around for a sample
 >>  > >  >>  circuit in the databooks, but they're there. Otherwise someone on
 >>  > the list
 >>  > >  >>  might be patient enough to walk you through a working circuit.
 >>  > >
 >>  > > I have looked and seen non in national book.... i can look again!
 >>  > >
 >>  > > And I agree on patience as question after  question on here needs
 >>  > answering and you could have a full time job just answering!
 >>  > >
 >>  > > Thanks!
 >>  > >
 >>  >
 >>  >--
 >>  >http://www.piclist.com hint: The PICList is archived three different
 >>  >ways.  See http://www.piclist.com/#archives for details.

 >>  --
 >>  http://www.piclist.com hint: The PICList is archived three different
 >>  ways.  See http://www.piclist.com/#archives for details.








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