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Why 0.1% resistors needed in opamp cct?

Discussion in 'General Electronics Discussion' started by eem2am, Nov 16, 2012.

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  1. eem2am

    eem2am

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    Aug 3, 2009
    Hello, the following is an opamp (differential amplifier) which is amplifying a sense resistor voltage by x100.


    http://i45.tinypic.com/72tvsi.jpg


    ....why are 0.1% resistors needed?....on the simulator, 1% errors in the resistors don't give big changes in op amp output.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Who said they were needed?
     
  3. eem2am

    eem2am

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    Aug 3, 2009
    I've heard lots of engineers (not at this forum) saying that 0.1% are needed.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Why do they say they are required?
     
  5. CocaCola

    CocaCola

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    What gauge and kind of wire or pc board traces do these so called engineers use that would not effect the accuracy of said resistors at that level? I mean seriously a few inches of traces on a PC board would whack a low value resistor all to heck at that level of accuracy...
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The point is, if experts on other forums have suggested this, then why hasn't this question been asked of them?

    I would be pretty amazed if I said something here and people on another forum were asked (rather than me) to explain it.

    Also, haven't I seen that schematic somewhere else? Is there another thread? Why is this a new thread? I'm thinking there may be relevant information in that thread. At the very least the OP could have provided a link back to it for background information.
     
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