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Op Amp Offset Voltage

  1. Mar 31, 2009 #1
    please

    can any one give me clearly information about Op Amp Offset Voltage

    with simple example and rule to explain that becaus i was found diffecalt to understsnd it .
     
  2. jcsd
  3. Mar 31, 2009 #2

    chroot

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    An op-amp in a feedback circuit should drive its two inputs to the same voltage. In reality, the amplifier will have some error, and the two inputs will settle at slightly different voltages. The difference in the two voltages is called the "offset voltage" or "offset error."

    - Warren
     
  4. Mar 31, 2009 #3
    ok thanks

    but can u give me any example with value of input and resistor and what the solution
     
  5. Mar 31, 2009 #4

    chroot

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    I have no idea what you're asking for. If you need help with a homework problem, please show us the problem (exactly as it was given to you), show us your work, and explain how and why you're stuck.

    - Warren
     
  6. Mar 31, 2009 #5
    i want to send patient tempareture

    so at first i have sensor (AD22100) with 10 degree range

    after that send the voltage of the sensor to VCO to convert v/f (TS902).

    but between the sensor and VCO i need op amp (741) but when i connect it the offset apper in the result and i am connect varaible resistor to the feedback of the op amp but i dont now how can i get the right result.

    not: u can see the data sheet if u want about sensor (AD22100),VCO(TS9402).AMPLIFIRE (741).

    THANKS
     
  7. Mar 31, 2009 #6

    chroot

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    Can you show us a schematic?

    - Warren
     
  8. Mar 31, 2009 #7
    who can i do that
     
  9. Mar 31, 2009 #8

    berkeman

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    How can you do that? If you have the schematic on your PC screen, you can press Alt-PrintScreen on most computers, and that will store a "screenshot" of the active window to the Windows Clipboard. Then go into an application like "Paint", and paste it in. Save it as a JPG file, or convert to PDF, and upload it here as an attachment (careful of the size -- there are limitations to upload file size). If the file is too big to upload, store it on an outside server or your own website, and post a link to it here.

    Also, with an older non-CMOS opamp like the LM741, there is a trick to minimize input offset current effects (which can be worse than input offset voltage effects on some opamps). When you show us your schematic, we can look to see if you are using this trick correctly.
     
  10. Mar 31, 2009 #9
    For open loop

    Vout = A{V+ - V- - Voffset]

    If you build a voltage follower with gain of 1 (wire from Vout to V-), and ground the positive input, the output voltage is equal to the offset voltage.
     
    Last edited: Mar 31, 2009
  11. Mar 31, 2009 #10

    i dont software to draw this circut can u give me one
     
  12. Mar 31, 2009 #11
    and i need example to show me the mean of offset please
     
  13. Apr 1, 2009 #12

    berkeman

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    Google is your friend. Learn to use it. I Googled the following (type it in the Google search box):

    opamp input offset voltage tutorial

    And Google came back asking if I meant:

    op amp input offset voltage tutorial

    to which I answered OK. Here is the hit list:

    http://www.google.com/search?hl=en&...=op+amp+input+offset+voltage+tutorial&spell=1

    There are many good hits, including a tutorial on your LM741 opamp (that's how I usually spell opamp, not op amp) as the first hit. Hope that helps.
     
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