Non Inverting Amplifier

Hari Thazhe Oyyoth

Hi,

The gain of non inverting amplifier is (1+Rf/Ri).May I know from where the term "1" comes in that equation. This was a question asked me in one interview and my answer was "virtual ground". But the interviewer want either physical or intuitive explanation for that question. Please help me.

Thanks&regards

Hari

over 8 years ago

0 Pete%20Semig over 8 years ago

TI__Mastermind 25805 points

Hello Hari,

Please see the following figure. The underlying concepts are properties of an ideal op amp and a voltage divider. I leave the simplification of the equation as an exercise for you.

0 Hari Thazhe Oyyoth over 8 years ago in reply to Pete%20Semig

Intellectual 380 points

Hi Pete,
Thank you very much. Mathematical derivation I know but what I would like to have a physical or intuitive explanation(without mathematics).
I would like to know why the extra term "1" is coming for non inverting amplifier gain equation and why it is not coming for inverting amplifier gain equation without any mathematics.

Regards
Hari

0 Pete%20Semig over 8 years ago in reply to Hari Thazhe Oyyoth

TI__Mastermind 25805 points

Hello Hari,

Try asking yourself a different question, such as "Why can't the gain of a non-inverting amplifier be less than 1V/V?" Keep in mind the properties of an ideal op amp (e.g. virtual short across the inputs).

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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Non Inverting Amplifier