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  #1  
Old 04-25-2011, 03:01 PM
E&C Genius E&C Genius is offline
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Default Input Bias Current & Offset Voltage measurement of an op amp

Hello,

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.
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  #2  
Old 04-25-2011, 03:09 PM
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beenthere beenthere is offline
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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?
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Old 04-25-2011, 10:23 PM
wmodavis wmodavis is offline
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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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