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LM139A: LM139A Input characteristics

John Vranes
Intellectual 590 points
Part Number: LM139A
Other Parts Discussed in Thread: LM339

Hello.

I have some questions regarding the datasheet/specifications for the LM139A comparator.  They seem similar to other questions that have been asked, so please bear with me, as I'd like to ask them in a slightly different way.

1) Is the max differential input voltage or input voltage range indeed a static maximum of 36V?  Or is it actually tied to the value of VCC somehow (which seems common to other comparators)
2) I'm confused some by the common mode range and its accompanying note 3.  Do both inputs (or rather their average) need to be lower than the common mode range of VCC - 2V for proper operation?  Or is it true that, for proper operation, one input can go much higher than that as long as one input stays within the common mode range?

Thanks,
John

  • 0
    TI__Mastermind 49896 points

    Hello John,

    1. The inputs may be taken up to 36V, regardless of the supply. So they are an "absolute" number, referenced to the GND pin. This does not mean the output will be correct, but they will not be damaged.

    2. The maximum recommended input voltage is Vcc-2 to cover the temperature range. As long as one input is within range, the output will be correct. But the specifications (offset, prop delay, bias current) are not warranted.

    Please see the LM339 family Application Note, section 2.2 - all your questions will be answered in excruciating detail:

     http://www.ti.com/lit/pdf/snoaa35