resending.. looks like the image couldn't be attached, I will provide a lin=
k instead.

---

Hello,
when you have an Op Amp based differential circuit, like this:

http://t2.gstatic.com/images?q=3Dtbn:ANd9GcQWhPDqAhhrvFtX2sKPlIWHn5U8SybJXo=
_G32dm2KFPaQoHofQM

R1 should be =3D R2, and Rf should be =3D Rg, else asimmetry will arise.

Now, as gain is calculated as Rf / R1, a problem arises: if I want a gain o=
f 1 (of
course using a unity-gain stable OpAmp), what is better to use 100k ohm for=
 all 4
resistors, or 10k ohm? It's a CMOS OpAmp, thus high impedance.

I mean what are the pro's and the con's of using low value or high value re=
sistors?

What I'm mostly concerned is to minimize noise picked up, but as the OpAmp =
will be
often saturated and not by little (the OpAmp I'm using, MC601, doesn't do o=
uput inversion
when overdriven, and can tolerate some mA's of input current). If using 100=
k resistors
doesn't worsen the noise, then I will use it, as a further mean of input pr=
otection against
overvoltages, but if it has to worsen the noise picked up, I better don't. =
Any hints will
be very appreciated.

Thanks!
Mario

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.