Electronic Devices - Op-Amp Applications - Discussion

Discussion :: Op-Amp Applications - General Questions (Q.No.4)

4. 

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

[A]. 0 V
[B]. –2 V
[C]. 1 V
[D]. 2 V

Answer: Option B

Explanation:

No answer description available for this question.

Saumil said: (Feb 9, 2011)  
Vo = (-RF/R1)V1 + (1+(RF/R1))V2'
= -1 + (1+1)(20*V1/40)
= -2 (ACCORDING TO ME..)

Sumit said: (Nov 4, 2011)  
v0=(-rf/ri)(v1-v2)

Shri said: (Nov 30, 2011)  
v0=(1+rf/ri)*v1+v2 ......v2=0

Bhavik Desai said: (Feb 11, 2012)  
Vo = (-RF/R1)V1 + (1+(RF/R1))V2'
= -1 + (1+1)(20*V2/40)
= -2 (ACCORDING TO ME..)

Ananth said: (Feb 15, 2012)  
Simulation result says -2v.

Mallik said: (Mar 26, 2012)  
Answer is -2v..

write the equations for the circuit using KCL...
let say both the terminals of op-amp are at common voltage Vb.

now equation for first combination containing V1:

[{(V1-Vb)/100k}+{(Vo-Vb)/100k}]=0.
=> V1-2Vb=-Vo --------- (1)

now equation for second combination containing V2:

[(V2-Vb)/20k] = [(Vb-0)/20k]
=> Vb=V2/2 ---------- (2)

from 1 & 2
-Vo= V1-V2;
V0=V2-V1;
Vo= -1-1
=-2v

Murad said: (Apr 25, 2012)  
By using superposition principle:
Vo'=-(rf/r1)V1=-1V
Vi+= -1(20/40)=-0.5V
Vo''=(1+rf/r1)Vi+=2*(-.5)=-1
Vo=Vo'+Vo''=-1-1=-2V
So the answer should be B.

Raj said: (Jun 3, 2012)  
Vo'=-(rf/r1)V1=-1V
Vi+= -1(20/40)=-0.5V
Vo''=(1+rf/r1)Vi+=2*(-.5)=-1
Vo=Vo'+Vo''=-1-1=-2V
So the answer should be B.correct

Savitri said: (Oct 9, 2012)  
Vo=rf/r1(v2-v1).

Vo=100k/100k(-1-1)=-2.

Shakthivel said: (Jul 5, 2013)  
Vo = RF(V2-V1)/R1.

Vo = (-1-1)100k/100k

Vo = -2.

Dhanabal said: (Jul 20, 2013)  
/* The above example -v(inverting terminal) get more voltage than +v(non inverting) terminal*/

Vout = (v1-v2) * (-(rf/r1)).

= (1-(-1))*(-(100/100)).

= -2*1.

= -2.

Neetu Khadaria said: (Feb 24, 2014)  
Since its a circuit of subtractor whose o/p voltage is = v1-v2= -2*v2 = -2*1 = -2.

Youmna said: (Apr 25, 2014)  
R1 = 100K.
R2 = 100K.
Vo = R2/R1(V2-V1).
Vo = 100K/100K(-1-1).
Vo = 1(-2).
Vo = -2 Answer.

Atul Raghav said: (Nov 28, 2014)  
Vo = (-100k/100k)*1+(1+100k/100k)*{(-1)*(20k/(20k+20k))}.
= -1*1+2*(-1)/2.
= -1-1.
= -2 Answer.

Punam said: (Jan 28, 2015)  
Vo = -(Rf/R1)(V1-V2).

Miss said: (Apr 10, 2015)  
Vo = -Rf/R1*V1-V2.

= -100/100*1-(-1) V.

= -2 V.

Bayan said: (Oct 29, 2015)  
Why v2 negative?

Kiran Borude said: (Jan 29, 2016)  
Opamp have one positive terminal & one negative terminal. That's why it is called one terminal is inverting & 2nd is non inverting.

Shawn said: (Feb 19, 2016)  
I think the answer should be 0 V.

Because the is not powered. So no amplification.

Surya said: (Feb 28, 2017)  
It is diff amplifier Vo = (v2-v1) = (-1-1) =-2.

Sugin V said: (May 2, 2017)  
Here, V2/2 (1+Rf/Rs) + V1 (-Rf/Rs).

Rakesh said: (Oct 7, 2017)  
Vo=(-100/100)V1+(20/(20+20))((100+100)/100)V2.
Vo=-V1+(1/2)(2)V2.
Vo=-V1+V2,
Vo=-1+(-1) because -V2=1 => V2=-1,
Vo=-2 Volts.

Ali said: (Nov 2, 2017)  
(20/20+20)(100+100/100)*V1-(100/100)V2 = V1-V2.

The resulting output voltage is seen to be the difference of the two input voltage.

David Khasu said: (Aug 4, 2018)  
Here, we can use {Rf÷R1}*(v1-v2).

Avi said: (Mar 18, 2019)  
[R3/(R1+R3][(R2+R4)/R2][V1]-[V2 (R4/R2)] is the formula. So it is 0V.

Shrestha said: (Jun 3, 2019)  
According to the differential amplifier fromula:

Vout = (R2/R1)*(V2-V1).
= (20/20)*(-1-1).
= 1*-2 = -2.

Praveen said: (Jun 21, 2019)  
Vo = (-RF/R1)V1 + (1+(RF/R1))V2'.
= -1 + (1+1)(20*V1/40),
= -2.

Vaibhav said: (Oct 7, 2019)  
Simple and easy the circuit shown acts as a difference amplifier and output voltage is given by vo =( v2-v1)x(Rf/R1).

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