how to calculate the opamp offest influence to the output voltage

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shanmei

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Why the output voltage=1001 Vos？ Thanks

 

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It shows you right on that picture, VOUT=(1+Rf/Ri)*VOS
(because true VIN = imposed VIN differemce (GND) plus VOS).
The basic noninverting closed loop gain equation.
 

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    shanmei

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The figure is quite self-explanatory: Offset at the virtual ground -> non-inverting amplification of the offset -> G = 1 + (R2/R1) = 1001. Vo = G*Offset.
 

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    shanmei

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Do you mean the Vos applied to the negative input of the opamp, it is also equivalent to apply Vos to the positive input of the opamp?
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But the offset is applied to the negative input of the opamp, not the positive input of the opamp
 

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Due to feedback, the voltage at input(+) = input(-). Therefore, you can place Vos in either input, and the result will be the same.
 
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