OpAmp - Differential Amplifier with common mode noise

107

01:30:10

In this configuration the OpAmp works as a differential amplifier.

The common noise present in both signal ( represented by the sine waves) is cleared by the high common mode rejection

Normally R1=R3 and R2=R4 to facilitate the design and minimize the influence of bias current.

In this case:
  Vou = (V+ - V-)*(R4/R3)

In this example R4 is the resistor of 20k and R3 the resistor of 10k.

Ps .: This simulation use DC signals because it's easier to see the numerical results and check with the formula. You can change to sine or square wave if prefer.

published 9 years ago

zorgrian

9 years ago

It seems that in 'this example' you have created an amplifier that does nothing! Unless, it was you intention to demonstrate nothingness? Maybe you intended that the two signal generators represent the common mode noise? If this is the case then maybe you should say this? Please see my example of the same idea

zorgrian

9 years ago

Apologies, upon reading your description more carefully it seems that you do say that the signals coming from the generators and voltage displacement configuration, are indeed a representation of common mode noise... However my example is another take on this. So It shows both working differential amplification and common mode rejection...

agaelema

9 years ago

Why nothingness? He is amplifying the difference between the two signals and canceling the common mode noise simulated by sinusoidal sources. You said this because I applied DC signals on inputs?

agaelema

9 years ago

I have used the DC signals because it's easier to see the numeric results. The user can switch the sources to sine waves if prefer.

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