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LM2903-Q1: Common-Mode Input Voltage Range

Shinichi Yokota
Genius 9715 points
Part Number: LM2903-Q1
Other Parts Discussed in Thread: LM339

Hello,

I noticed the following description on LM2903-Q1's VICR - Common-mode input voltage range in the version H of the data sheet (SLCS141H).

It implies the inverting and the non-inverting inputs of the LM2903-Q1 are asymmetric. Is it correct?

If they were symmetric in terms of input structure, the description would be, "The upper end of the common-mode voltage range is VCC - 1.5 V for one input, and the other input can exceed the VCC level; the comparator provides a proper output state."

Best regards,
Shinichi Yokota

  • 0
    Intellectual 420 points

    A problem with some amplifiers is output inversion when outside the acceptable common mode range.  I believe it's that same effect that this comparator is speaking about.

    The note explicitly states "the comparator provides a proper output state" under the conditions.  The note isn't about device protection but about the acceptable Common-mode input voltage range, VICR.

  • 0
    TI__Guru 52556 points

    Shinichi-san,

    Please see section 2.5 of the LM339 family application note:

     https://www.ti.com/lit/an/snoaa35a/snoaa35a.pdf

    The input voltage range applies to *each* input. As long as one input is within the valid input voltage range, the output will be correct.

    "Common mode" is not really a correct term for comparators since the inputs are rarely kept at equal potentials. The limit must be applied to *each* input independently.