Properly grounding/terminating unused Op Amps?

[slashandburn]

I'm digging back in after yet another sabatical and as usual, it would seem I've returned a few braincells lighter and full of doubts.

Say I'm only using one half of a dual op-amp and I don't just want to leave the unused half floating, is the correct way to terminate the unused side simply to ground the +input2 and/or link -input2 with output2?

Cheers in advance. Apologies for the crap question that's likely been answered a million times before.

[stonerbox]

http://www.electronicproducts.com/Analog_Mixed_Signal_ICs/Amplifiers/Properly_terminating_an_unused_op_amp.aspx

Figure A. Way, way down on the page.

[R.G.]

The electronicproducts link gets it right after some discussion.

An opamp that is unity-gain stable will always be OK if it is connected as a follower, and its inputs are within its input common mode range. The input common mode range will always contain the middle between the most-positive power supply to the chip and the most-negative power supply to the chip.

So tie the output to the inverting (-) input to make it a gain-of-one follower, and tie the non-inverting (+) input to a voltage that's always in the input common mode range. Good choices are the bias supply for the other (used) sections of the opamp, or simply the non-inverting input of one of the other opamp segments.

[EBK]

I asked a related question once, and perhaps it is one you should consider.  I believe the best way to wire up an unused op amp is to come up with a way to use it. 
http://www.diystompboxes.com/smfforum/index.php?topic=115935.msg1071746#msg1071746

[Kipper4]

Haha Eric was a lurker......

[EBK]

Haha Eric was a lurker......

And, I really thought I posted that over a year ago.  Turns out I've been a recovering former lurker for less than 6 months!

[slashandburn]

Brilliant, thanks!

I'll give the article a proper read over, I'm not sure I'm fully grasping the reasons for this. Following RGs advice then I'd actually making it a unity gain follower, rather than just trying it up into redundancy? I guess that makes sense and even covers Eric's suggestion of finding a way to use it.

My motivation for using a dual was thinking it would suit a perf layout better. That and it would allow me to procrastinate rather than build!

Thanks again. Seems I've more procrastinating to get done.

[PRR]

> I'm not sure I'm fully grasping the reasons

If you do not TELL an opamp what to do, it will do what it likes.

If you need one dog to guard the flock, but dogs come in pairs, you sure better do something with the other dog or there will be trouble.

In opamps, often this is singing in MHz. May not be directly audible, but will leak all over the box, will intermodulate down to the audio band, may also run-up power current (stages that "work" at MHz sometimes get greedy doing so).

[Passaloutre]

On an orange squeezer could I just ground the second + input and tie the - Input and output together? Would I be better off using it on the + 9v rail? Using this layout:

[bluebunny]

I would short pins 6 and 7 (to make a unity gain "buffer", as R.G. said) and tack a jumper from pin 3 to pin 5.