Electronic Devices - Op-Amp Applications - Discussion

Discussion :: Op-Amp Applications - General Questions (Q.No.8)


Determine the output voltage when V1 = V2 = 1 V.

[A]. 0 V
[B]. –2 V
[C]. 1 V
[D]. 2 V

Answer: Option A


No answer description available for this question.

Divya said: (Dec 12, 2011)  
The given ckt is a differential amplifier ckt.

Mallik said: (Mar 26, 2012)  
Assume common voltage at two terminals to be vb; lets write KCL for the ckt

[(v1-vb)/100k]+[(V0-Vb)/100k]= 0;
[(V2-Vb)/20k] = Vb/20k;

=> V0 = V2-V1;

Sunil said: (Jan 4, 2015)  
What we are talking about is op-amp?

Which amplifies the difference between two signals?

Here, difference between two signal is 0(v1-v2). And also, the CMRR Common Mode Rejection Ratio.

Gurpreet said: (Jul 15, 2015)  
@Sunil brother in actual practice v1 and v2 are not equal but nearly equal.

Ezhil said: (Jan 16, 2017)  
Consider the nodes after two input resistance as v3.

Bby using node analysis method.

(v3-v1)/100k + (v3-vo)/100k =0-----(1).
(v3-v2)/20k + (v3/)20k =0--------(2).
Sub v1=v2=1 in above equatios.
We get v3= 1/2 sub this in equ 1.
ve get vo =0.

Rajan said: (Apr 29, 2020)  
I think the answer is 1v (by virtual short method).

Because both the input resistor and feedback resistor are unequal hence we cant apply standard differential op-amp formula Vo= Rf/Rin(V2-V1).

Abhi K said: (Aug 14, 2022)  
I think the answer should be,

If we apply both inverting and non-inverting formulas.
Then multiply by (V1-V2).

(-Rf/R1) + 1 + (Rf/R2) * (V1-V2).
(-100/100)+ 1 + (100/20) * (1-1).
= 0.

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