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LM293: Why does the datasheet give conflicting information on the comparison polarity???

John Fenley
Prodigy 150 points
Part Number: LM293

In the datasheet for the LM293 and other variants of this comparator, Section 7.3 states:

The output NPN will sink current when the positive input voltage is higher than the negative input voltage and the offset voltage.

In the same datasheet, section 8.2.2.1 states:

If IN- is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking current

I find this odd.  And by 'odd', I mean really conflicting.

Please explain.

  • 0
    TI__Guru 50236 points

    Hello John,

    Yes. We are aware of this. We have corrected it and the revised datasheet should be released soon.

    Below is the updated text:

    The following is a list of input voltage situation and their outcomes:

    1. When both IN- and IN+ are both within the common-mode range:

    (a) If IN- is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking current.
    (b) If IN- is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is not conducting.

    2. When IN- is higher than common-mode and IN+ is within common-mode, the output is low and the output transistor is sinking current.
    3. When IN+ is higher than common-mode and IN- is within common-mode, the output is high impedance and the output transistor is not conducting.
    4. When IN- and IN+ are both higher than common-mode, the output is low and the output transistor is sinking current.