# How to convert CMRR in DB to Numerical Value

1. ## How to convert CMRR in DB to Numerical Value

My CMRR value is 90dB. Can anyone explain to convert this in numerical value.  Reply With Quote

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2. ## Re: How to convert CMRR in DB to Numerical Value

90 dB = 20 * log(voltage_ratio)
=>
voltage_ratio = 10^(90/20) = 31623

The output will change max 1/31623 of the input common mode change. In this case about 32uV/V

You can also get this directly by going from out/in = -90 dB = 10^(-90/20) = 32u  Reply With Quote

3. ## Re: How to convert CMRR in DB to Numerical Value Originally Posted by satiz My CMRR value is 90dB. Can anyone explain to convert this in numerical value.
20*log(x)=90dB
so , x is 31633.  Reply With Quote

4. ## Re: How to convert CMRR in DB to Numerical Value

Hi,

What about doing an internet search on your own: "online dB calculator"...

Klaus  Reply With Quote

5. ## Re: How to convert CMRR in DB to Numerical Value

Online calculator gives me the results. But Mr.std_match explanation is very much useful to understanding better way :)  Reply With Quote

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