(2) dirty/clean ground again [sdiy]

harry harrybissell at prodigy.net
Tue Aug 20 06:07:43 CEST 2002


You just extend the same idea of the loading... if you know the load will be
10K ohms... then even 100 ohms in series with the leads seems like a small thing...
but you then need more capacitor, because during light loads the supply at the
opamp pins will float up... then down during high loads... this might modulate
the opamp output... ;^(

The RC constant should be long enough to filter out any hum on the supply...
I usually use 10 - 100 ohms and as much cap as I need

I don't usually go with series resistance except for really critical high gain
stages like preamps that could amplify EVERYTHING.   Sort of a last resort.

I also like shunt regulators for individual stages like opamps... sometimes.
A local +/-10V supply instead of a more dirty +/-12 can help a lot.

H^) harry



Scott Gravenhorst wrote:

> harry <harrybissell at prodigy.net> wrote:
> >I say decouple positive and negative busses to ground with caps. Better if you
> >can stand series resistance in the supply lines as well...
> >
> >H^) harry
>
> This is an interesting technique.  For something like opamps, is there an
> optimum series resistor(s) value?  Does that vary from opamp type to opamp type?
>  My guess is yes and it has to do with how much current the opamp can supply and
> how much the designed load will to draw at maximum.  Are there applications
> where one ought not do this?
>
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