Re: LF: 16 bit vs 24 bit ADC?

[Andy Talbot <andy.g4jnt@gmail.com>]

When you add non coherent sources like noise, you have to add power,
or mean square values.
So a Noise voltage of  RMS = 16  (the input noise) added to noise of
RMS = 1   (Nq)
= SQRT(16 * 16 + 1 * 1)  = RMS noiise voltage
but power = RMS Squared,

So ignoring the SQRT and taking 10.LOG of the sum of squares goes
direct to the answer in dB

And resistance is always assumed to be unity in relative calculations
like this - everything is normalised.

Andy
G4JNT


On 3 December 2011 13:29,  <jcraig@mun.ca> wrote:
> Hi Andy,
>
> A silly question from someone struggling to understand,  but the ^2 below,
> 20log... and V^2/R (for ex)  are all related ?  We're looking at voltages
> and comparing powers?
>
>
>> noise, it will increase the overall in the ratio
>> (1 + 16^2)  / 16^2 = 257 / 256 or by about 0.017dB.
>>
>
> Joe vo1na
>
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