[sdiy] Which opamp pins wiring is best for CV out ?? A , B or C ???

[Neil Johnson]

Hi,

Harry wrote:
> hmmm... when that input is on the end of a shielded cable. I've had LOTS of TL07x (08X)
> opamps go NUTS when driving even a reasonably short cable, if there is no series resistance.
> Even 10 ohms is enough to decouple the capacitive load...

Yes indeed, those darn cables!  If we imagine a typical example:
output goes to a connector on the front panel.  This then goes into a
cable, lets assume shielded cable for those who like to use jacks.
Now I've seen cables a good couple meters long on modular systems
here.  Then that plugs into something else, which might be a passive
multi, that then breaks out to a couple more one-metre cables.  So,
load capacitance?  Looking at the VanDamme catalogue I see something
of the order of 100-160pF/m.  How many metres?  Lets say 4 (2+1+1).
So that's 400-640pF.

That's a lot of capacitance for a lowly op-amp to drive without going "NUTS".

Cheers,
Neil
-- 
http://www.njohnson.co.uk