Inverting opamp: why a resistor between + and ground?

[Skreddy]

Is it just to increase the input impedance?  Does it "do" anything?

Example: look at the Rebote Delay (v. 2 and 2.5) at Tone Pad.

[R.G.]

In circuits which require DC accuracy, having an equal resistance between + and its bias voltage and - and wherever it gets its voltage minimizes the offset on the output caused by the input currents flowing through unequal resistors. That is - it's for DC accuracy, and may be used or not used in AC circuits.

[Skreddy]

Ah, okay.  Cool; thanks for the info!  I'm not so much up on the DC side of things.  Or opamps. heheh

Ha, I learned the other day that you have to reference a signal to virtual ground (as opposed to actual ground) if you're going to an opamp without using a capacitor.  Geez, I sound like such a noob.      I have to constantly water my brain with new information, and eventually it begins to absorb.

[The Tone God]

Check out the "Opamp-eration" article at the site.

Andrew

[Skreddy]

Thanks; yeah I read that page the other day.  Very helpful; thank you!

I looked up a few words on Google to help solve a problem, and I came up with a very nice Texas Instruments document about opamps yesterday.

You may have seen this, but I'm sure there are lots here who haven't...

http://instruct1.cit.cornell.edu/courses/bionb440/datasheets/SingleSupply.pdf

--Lots of great info and basic circuit examples.