As you all know, most Inst. Amp. examples on the Internet have a 'Differential Amplifier' part as shown below.

But, what would happen if a summing amplifier was used instead ? What kind of disadvantages I would have ?

Noise elimination and gain are very similar like Diff. Amp. does if my calculations are correct.

Any comment will be appreciated. Thank you for your consideration.

enter image description here

  • 1
    \$\begingroup\$ Um.. you would end up cancelling out your differential signal and amplifying the common mode noise instead... \$\endgroup\$
    – Trevor_G
    Commented Oct 12, 2017 at 15:26
  • \$\begingroup\$ I think you need to look up the core reasoning in using a differential amplifier (differential mode amplification, common-mode rejection) \$\endgroup\$
    – Joren Vaes
    Commented Oct 12, 2017 at 15:29
  • \$\begingroup\$ "... if my calculations are correct." Let's see the calculations! See my answer to electronics.stackexchange.com/questions/332390/… which may help. \$\endgroup\$
    – Transistor
    Commented Oct 12, 2017 at 19:33

1 Answer 1


With a differential amplifier you are removing the noise and amplifying the signal. With a summing amplifier you are removing the signal and amplifying the noise. This might be useful in some exotic application, but certainly not common.


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