Doubt in a numerical problem on differential amplifier circuit

[ujjwalkapil]

Hi all,

I am having a doubt in a question on differential amplifier that I have posted as an Image. I was able to solve for the output voltage correctly but my main doubt is

input voltage(2 mv) ≠ drop across 20 kΩ resistor+ drop across 43 kΩ resistor (why not equal ?)

 

[KlausST]

Hi,

in this circuit there is no need for the voltages to be equal.

The sum of currents must meet.

Klaus

 

[LvW]

Hi all,
I am having a doubt in a question on differential amplifier that I have posted as an Image. I was able to solve for the output voltage correctly but my main doubt is
input voltage(2 mv) ≠ drop across 20 kΩ resistor+ drop across 43 kΩ resistor (why not equal ?)
View attachment 110620

In your "calculation" you have forgotten the influence (voltage drop) caused by the current source.

 

[ujjwalkapil]

I could not understand. Why is there no need of the voltages to be equal? would that not be a violation of Kirchhoff's voltage law?
I am really sorry. This is the first time I am studying amplifiers(1st year engg) and some concepts may be new to me. Please explain a little bit.