Stablising unused op-amps

[chromesphere]

Hey guys, messing around with some simple dual op-amp circuits and had a small question.  Whats the 'correct' method for tying down an unused op-amp to prevent cross-talk?  I see some people connect them to ground, where as others connect inv and non-inv pins together, and the output only to ground.  Is one method preferable to another or does it not really make much difference?
Thank you in advance
Paul

[oldhousescott]

I think I'd tie the output to the neg input, and tie the pos input to AC ground. I wouldn't tie the output to anything low impedance.

[stecykmi]

I think I'd tie the output to the neg input, and tie the pos input to AC ground. I wouldn't tie the output to anything low impedance.

agreed, this is what i do.

[alanp]

IIRC, tie output to neg input, and tie pos input to 1/2 the ic's operating voltage.

[chromesphere]

Cheers dudes! I originally had them all tied to ground but will do as suggested, seems like the more sensible approach.

[sturgeo]

As a picture is worth a thousand words...

[chromesphere]

There seems to be a difference of opinion here.  The above picture connects the positive input to ground whereas Alanp and others have suggested connecting it to vbias, 1/2 of the supply.  Much of a muchness?  Ground would actually be infinitely more convenient routing wise.

[sturgeo]

Certainly don't take my word for it, i'm relatively new to the pedal building game!

I've used the above in a build without any adverse affects, i must've seen it in a schematic somewhere 

[alanp]

http://pdfserv.maximintegrated.com/en/an/AN1957.pdf

Tying an input to ground and linking the other input to output causes the opamp to draw more current, according to this. Figure One, correct way, is what I said (nice to see the memory isn't wholly gone yet.)

[sturgeo]

I stand corrected

I've seen the method i posted in Wampler & Rockett pedals i believe, well peoples traces of them

[oldhousescott]

If your design has equal plus and minus rails, then you can tie it to ground. In any case, as stated above, you want it tied to the midpoint between the plus and minus rails. This is often (but not always) Vbias.

[jubal81]

I started the nerd's corner thread a while back with this nugget:
http://www.madbeanpedals.com/forum/index.php?topic=8630.msg74763#msg74763

[rullywowr]

Absolutely correct. This site is great http://www.analog.com/static/imported-files/rarely_asked_questions/unused_op-Amp_article.html

[chromesphere]

So nice to get a clear answer to this sort of technical question!  Thanks so much!