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Isha Lohan posted an Question

May 21, 2020 • 16:43 pm

30 points

IIT JAM
Physics (PH)

Q the output voltage vo ot the opamp circuit given below is-

JAM 2016 Q48. Acc to me answer should be zero, but in official answer key it is given to be 6V?

3 Answer(s)

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Chandra prakash

You can reasonably assume that currents can flow from an input (Va in your diagram) and from the op-amp output (Vo in your diagram). This means you can assume current does not flow into the two op-amp inputs and these can be regarded as high impedances ..
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Abhishek singh Best Answer

As V1(non inverting terminal) is grounded. That means the output will be zero, because the amplification of zero by any factory is zero itself. regards.
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Dhairya sharma

see another explanation.
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i hope dear now u get it.
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because o/p has infinite i/p impedance
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yes input current in opamp is zero.
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yes dear,you got it .👍
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Chandra prakash

see attached file dear... it's explanation of this type of prob..... I hope u understood it
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in attached file the non inverting terminal is not grounded. but in given ques non inverting terminal is grounded
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Abhishek singh

A general solution. It would help you in solving similar questions too. regards
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how can I help you?
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ye thik h , but question m ground diya hua h non inverting terminal pr
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Then the answer should be zero! I had not looked at it carefully. sorry for the inconveniences
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I also think answer to be zero this way. but in jam official answer key it was given 6V. Is it wrong there?
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if you have seen in the jam official answer key(with the same diagram) then I couldn't make a statement against the official key. But still, in my opinion the answer should be zero.
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non inverting terminal is not grounded
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in your attached question
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Chandra prakash

dear see attached file... I hope it's helpful for you dear..
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Dhairya sharma

see attached solution. output will be 6 coz Vb= Va
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while calculating potential at A, why do we add up all the current to zero? current must flow down to ground?
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incoming current = outgoing current. from nodal analysis
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dear current in ground is 0
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how is current in ground zero? current flow from high potential to low potential so all current should go down through ground
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dear.....i attached a pic ...see that. it's a concept and thumb rule that no current will flow in op/amp.
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current not flow in two input terminal bcoz of high impedance
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yes the input current in opamp will be zero. I was doutfull, about if all the current will flow down to ground.
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Ruby negi

non inverting case..I used this formula(or concept)..
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okay, thanks
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Ruby negi

6 is the ans.
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here, in calculating V01, how do you put the other two resistance in parallel (R3 in formula). the other two resistances are at different potentials, can we add then in parallel?
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