Comp caps in NE5534?

JDMcEachin jdm at synthcom.com
Wed Jan 22 22:03:56 CET 1997


At 05:24 PM 1/22/97 MEZ-1, Daniel Oberfeld wrote:
>Hi!
>> 
>> >BTW, if you use the NE5534, don't forget to use external
>> >compensation capacitors. (Maybe you can just leave the 301's
>> >caps in, but please check this.)
>> 
>> EEEEK!!!

Sorry Mark, I thought that an internally compensated opamp didn't need
compensation caps, but it seems there are some that do to get audio
bandwidth, including the 5534.  Doh!  Live and learn.  If you do use the
5534s (I can't see any reason why not), then DON'T clip the compensation
caps.  These are there to extend the bandwidth, and I think they're about
the right size.  The worst you could do would be to install some opamps and
listen to them (like on the output board - the one on standoffs on the far
right), and if they don't allow the filter freq to go out past your hearing
range, then replace them w/ LF411s.  I KNOW the 411s work.
 
>I have no clue exactly *where* in the S/H you want to use these amps, 
>but if it's the stage next to the hold-capacitor you need of course a 
>very high input impendance to avoid excessive drift+droop - in other 
>words some FET or even MOS (CA3140) input stages!!
>NE5534 wouldn't do here,  I guess.

Mark isn't the one w/ the S/H problem, but he will be replacing all his
opamps, including the ones in the S/H.  The S/H circuit has FETs that render
these points moot - i.e. the 5534 is ok to use (it's replacing an LM301,
remember).

You know, I think I'm actually beginning to understand some of this opamp
stuff. My opamp prof in college was always too concerned w/ being able to
make a good Bode plot, never enough about real world opamps...

JDM




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