Input Bias Current & Offset Voltage measurement of an op amp

Discussion in 'Homework Help' started by E&C Genius, Apr 25, 2011.

  1. E&C Genius

    E&C Genius Thread Starter New Member

    Dec 9, 2009
    Jeddah, Saudi Arabia

    I want to measure the Input Bias Current and the Offset Voltage of an op amp for my electronics lab experiment. I tried to design a circuit for that purpose but it didn't work on (Multisim software), so obviously I didn't build it.

    I've found this PDF online; and as you can see on page 4 it suggest a way to measure them. But I couldn't understand how exactly can I do it?

    Please help me with a suitable circuit or an explanation for the one in the PDF.

    Thank you.

    Attached Files:

  2. beenthere

    beenthere Retired Moderator

    Apr 20, 2004
    Missouri, USA (GMT -6)
    Figures 4 & 5 in the article describe how to measure the input bias current. It looks as if all you need to do is to duplicate the setups given in the file. really nothing to design.

    Can you be specific about what is causing you difficulty?
  3. wmodavis

    wmodavis Active Member

    Oct 23, 2010
    Colorado, USA
    The basic problem of measuring input bias current is:
    Because these bias currents are so miniscule they defy direct measurement. You cannot simply insert an ammeter in series and get the measurement you want because the currents are virtually zero compared to those we usually measure. Just try to find a femto-ammeter. Therefore it must be measured indirectly and determined by calculation. Accuracy of the determination is dependent on many factors which must be carefully and accurately measured and controlled.

    Good luck.
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