LM13700: Can we leave the unused second operational amplifier (LM13700) pins floating

PAVAN P

Part Number: LM13700

Hello Team,

We are using LM13700 in our design for audio limiter application, we have not used the second operational amplifier. Can we leave the second Op-Amp pins Floating?

As shown in below screenshot can we leave the highlighted pins floating.

over 1 year ago

0 Gerasimos Madalvanos over 1 year ago

TI__Mastermind 29156 points

Hey Pavan,

Please see the following E2E post on how to configure your unused amplifier. Terminating Pin 16 to V- will ensure no bias current. The rest can be left floating.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/647049/lm13700-terminating-unused-ota

Best,
Jerry

0 Clemens Ladisch over 1 year ago

Guru 287370 points

Unused outputs can (and should) be left open.

In general, unused op-amp inputs should be properly biased. But see figure 16:

In theory, if you leave the inputs (pins 1,2,3,4,7) open, no current will flow. But they might pick up noise, so it would be safer to connect them to V−.

0 PAVAN P over 1 year ago

Prodigy 150 points

Thank you both for quick reply,

So, to summarize we can leave the output pin as floating (12,9), remaining inputs (10,13,14,15,16) should be grounded, such it can be prevented from noise pick on other amplifier.

What about Diode bias input(2,15) can we it as floating, does this pin also have effect on noise pickup.

0 Gerasimos Madalvanos over 1 year ago in reply to PAVAN P

TI__Mastermind 29156 points

Hey Pavan,

Diode bias is just a connection to the inputs through a diode, so it could still pick up noise but it will have ~0.7V less noise pickup than the input pins.

Best,
Jerry

+1 Ron Michallick over 1 year ago in reply to Gerasimos Madalvanos

TI__Guru**** 154086 points

Pavan,

The first reply is an acceptable solution. There are many other good solutions. The only 'bad' solutions are shorting outputs, connecting inputs out of normal range, and have open pins connected to long traces (antenna).

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LM13700: Can we leave the unused second operational amplifier (LM13700) pins floating