quad OP-amps

[Tony Clark]

> is there any major difference in the quality of quad OP-amps as compared
> to dual or even single packages?  I am just curious why anyone would use
> a TL081 type OP-amp when they could sqeeze so much more circuit per inch
> with say a TL084. 

   There shouldn't be.  The reason why most high end gear tends to use 
single op-amps rather than duals or quads is due to the amount of 
crosstalk that can occur between op-amps on the same substrate (i.e. in 
the same chip).
   Good op-amps tend to have really good levels of crosstalk isolation, 
typically 90dB or better (usually better than the overall noise level of 
final signal output).
   Now if you have a particular mono signal that passes through a series 
of op-amps, then I'd say it's perfectly fine to use a dual or quad.  The 
problem tends to be when you run signals in parallel.  For example, 
having a stereo signal pass through two op-amps on a single IC.  In this 
situation, the stereo channel isolation is WORSE than if you had used two 
single op-amp ICs (one chip per mono channel).
   Maybe someone else can explain it better than I if I haven't done it 
correctly.
   
   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://aupe.phys.andrews.edu/~clark
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