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What is input offset current (IIO) of an operational amplifier?

Latest Updated:12/01/2011

Question:

What is input offset current (IIO) of an operational amplifier?

Answer:

There is a difference in the input current that flows in or out of each of the input pins, even if the output voltage of the operational amplifier is 0 V, due to the fact the pair characteristics (hFE,VBE) of the differential transistor do not match. This difference is known as the input offset current (IIO).

IIO=|IB+-IB-|




The drop in voltage that occurs due to this different current flowing through the signal source resistors (RS) connected to the operational amplifier inputs causes the offset voltage to rise.

Note that the input offset current causes an error in the output value in the same way as the input offset voltage.
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