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Issues with nulling offset voltage

rizvi

Oct 27, 2017
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Oct 27, 2017
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hello dears..

i am trying to analyse op07d which is an ic for an operational amplifier. when i apply a biasing voltage of ±12 volts, ground both the input terminals, i get an output of 10.5 volts which is an offset but prety huge. as the data sheet suggests this value to be in microvolts. kindly help me out here. what i am doing wrong.
 

BobK

Jan 5, 2010
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The input offset is the offset at the inputs, not the output. Without feedback, that offset will be multiplied by the gain of the op amp, typically 100,000 to 100,000,000. In your example, the small offset voltage is being multiplied by the gain and the op amp is trying to output a voltage higher than it can, so it is going as high as it can go, which is 1.5V below the positive rail.

Once you add feedback to control the gain, the offset at the output will be much smaller.

Bob
 

rizvi

Oct 27, 2017
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Oct 27, 2017
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i tried using 4.7k resistors for both R1 and R2 making a gain of 1. and then i grounded both the inputs , still i was getting similiar results. i.e offset was trying to reach saturation.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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R1? R2? A gain of 1? Grounded both the inputs? What inputs? Post a schematic with parts labeled for identification during subsequent discussions: identify R1 and R2 on the schematic and post a value next to each label.
 

rizvi

Oct 27, 2017
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i will keep that take care of that in future @hevans1944
and thankyou bob. your point here led me to find my error.
thankyou all
'
 

Aftabalam

Mar 3, 2019
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Mar 3, 2019
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hello dears..

i am trying to analyse op07d which is an ic for an operational amplifier. when i apply a biasing voltage of ±12 volts, ground both the input terminals, i get an output of 10.5 volts which is an offset but prety huge. as the data sheet suggests this value to be in microvolts. kindly help me out here. what i am doing wrong.
You should have to use some other op-amp IC's(other than Op-07) those who are having minimum offset voltage.T here are so many IC's available in the market. If you have issues of offset causing error in your result you should initially choose op-amp Ic tHe one having least offset.
 
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