# Input offset voltage

Discussion in 'Analog & Mixed-Signal Design' started by hp1729, Aug 16, 2016.

1. ### hp1729 Thread Starter Well-Known Member

Nov 23, 2015
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Let's say we have a non-inverting op amp circuit with a gain of 100 and an input offset voltage of 5 mV. A ground at the input would result in an output of 5 mV x 100 or 500 mV. Is that right?
An input pulse 1 mV high would still result in an increase at the output of 100 mV, right?

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Depending on the polarity of the offset the output could be +500mV or -500mV.
Right.

3. ### #12 Expert

Nov 30, 2010
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Now, try it as a comparator running with the gain at open loop.
Set the input offset voltage at + 5 mv for the first test and - 5 mv for the second test.

Then try some scenarios for different input bias current, input bias current offset, input resistors, different noise levels, and different frequencies.

4. ### crutschow Expert

Mar 14, 2008
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Just to be clear to the OP, the offset polarity and magnitude for a particular op amp device is generally random with a voltage limit as given in the data sheet.

5. ### hp1729 Thread Starter Well-Known Member

Nov 23, 2015
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True. I can see your point on a voltage comparator.

6. ### ramancini8 Member

Jul 18, 2012
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hp1729---What happens if the gain is 1000 on a 5V supply?

7. ### hp1729 Thread Starter Well-Known Member

Nov 23, 2015
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Good point there.