#### afr123

##### Junior Member level 1

I have a very basic question.

I want to calculate SNR at the output of the opamp. First I measured the rms value of the noise without any input using a digital oscilloscope. Then I input a sinusoidal input of 40kHz to the opamp. The voltage at the output was 0-5V.

So to measure the SNR I divided 5V by sqrt of 2 to get the rms voltage. Then I used 20*log (rms voltage / rms noise) to get the SNR.

My question is do the need to remove the offset (2.5V) from the signal first and then calculate the rms voltage? And secondly, is it the proper method to calculate SNR?

Regards