LM224A: What to do with the pins of unused op amps?

Venkatesh P17

Intellectual 895 points

Part Number: LM224A

HI TI team,

I am using the part LM224ADR, I used only one op-amp of this IC and there are 3 remaining unused op-amps.

1) What should I do with the pins of those op-amps?

2) Can I kept those are unconnected? Is the unconnected pins will make any problem with my design?

3) Can I proceed with this document?

Thanks and regards,

Venkatesh P

over 3 years ago

0 Michael Steffes over 3 years ago

Guru 47535 points

Yes, that is a good reference, here is another one,

https://e2e.ti.com/blogs_/archives/b/thesignal/archive/2012/11/27/the-unused-op-amp-what-to-do

0 Venkatesh P17 over 3 years ago in reply to Michael Steffes

Intellectual 895 points

Hi Michael,

Thanks for the response.

I will read out the link you suggested.

Can you please let me know that what happens if I left the pins unconnected? Will it cause to any serious harm?

Thanks and regards,

0 Tim Claycomb over 3 years ago in reply to Venkatesh P17

TI__Genius 15410 points

Hi Venkatesh,

I actually prefer this document over the one Michael recommends. While the one Michael recommends does have the correct configurations recommendations it does not discuss input connections directly to GND (we don't recommend doing this). Instead we like to see a series resistor between the input and GND.

Regarding leaving the pins unconnected, this is not recommended because this leaves the pins floating and in an unknown state. Its is best to configure the amplifier based on the recommendations in the app note.

Thank you,

Tim Claycomb

0 Michael Steffes over 3 years ago in reply to Tim Claycomb

Guru 47535 points

That new one is pretty thorough,

Personally, if I was doing a VFA unused channel I would probably put say 10kohm feedback R with 100ohms across the inputs with V+ at ground. Operating closed loop high noise gain with minimal load.

0 Michael Steffes over 3 years ago in reply to Michael Steffes

Guru 47535 points

Or actually, put the V+ pin to ground through say a 100ohm R.

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LM224A: What to do with the pins of unused op amps?