(2) dirty/clean ground again [sdiy]

harry harrybissell at prodigy.net
Tue Aug 20 05:06:30 CEST 2002


<everything prior snipped>

I submit (to the gentlemen and Cynthia of the jury ;^)

That very often the loads on an opamp DO indeed go to ground when using
a bipolar supply...and they are often greater than picoamps.

Case in point:  A potentiometer used as a "volume control" in a mixer circuit.

We use a reasonable value of summing resistor, maybe 100K so as not to get
too much noise... so that dictates a pot of maybe 1/10 that value so loading is
not
an issue... so 10K to ground.  We could be in the milliamps here...

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






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