LM2903B-Q1: un-used input pins

Josef Warta

Part Number: LM2903B-Q1
Other Parts Discussed in Thread: LM2904B, LM2904, LM2903

Hello Team, what would be a good recommendation how to handle un-used input pins for LM2904B? For example if there is only one op-amp used in a dual-package.
And reducing the quiescent current of the un-used op-amps.

For example:

Many Thanks

Josef

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Josef,

we are talking about the LM2904, not the LM2903, right?

For an unsed OPAmp I would do it this way:

The picture is from another thread.

Kai

0 Paul Grohe over 3 years ago

TI__Guru 53256 points

Hello Josef,

You are referring to two different part numbers, the LM2903, which is a comparator, and the LM2904, which is an op-amp.

Both have an Appnote discussing this very subject (and the images you posted are from the appnote):

Application Design Guidelines for LM339, LM393, TL331 Family Comparators

Design Guidelines for Devices with LM324/LM358 Cores

For these op-amp devices, choking off the input stage causes the output to rail, and for bipolar devices, slamming the output into the rail can increase supply current as current is dumped into the base of the output transistor. So the small current saved by choking off the input stage is lost in the railed output stage base current. You should bias it as Kai showed to keep the output from railing.

It makes little difference for the LM2903 comparator which way the output is biased.

0 Josef Warta over 3 years ago in reply to Paul Grohe

TI__Expert 4080 points

Hello Paul, sorry - was a typo in the text. Headline is right, it's a LM2903 topic. Many Thanks for quick answer and BR Josef

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LM2903B-Q1: un-used input pins