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SQNR of IDIAL vs non idial FLASH ADC

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yefj

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Hello, I have a formula for SQNR when we tale Half of the full scale and we do it for sinus input for some reason
but in FLASH ADC shown bellow we dont divide by half the FULL SCALE for SNQR.
Full SCALE=V_max-Vmin of the values possible to be recieved by the ADC
So when we divide by 2 and when we dont?
Thanks.

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To find SQNR you need the signal power. If your FSR is LSB*2^B, then to fit a sine wave in this FSR you need an amplitude of 0.5*LSB*2^B. Then, once you have the amplitude, the signal power is 0.5*A^2.
 

Hello Sutapanaki,given my FLASH can handle voltages from 0 to 1,
if my input is 0.5+0.5sint(wt) my signal goes from 0 to 1 as the voltage ladder of the flash ADC.
what is the signal power then?
do i still need to divide by 2 the "Vfs"?


In Vin=sint(wt) we have it from -1 to1
I dont know how to have those two case in FLASH ADC SQNR SIGNAL member.
Thanks.
 
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I dont understand the definition of SQNR, We have two ranges ,1. is the range pk-pk of the voltages which ADC can handle and the other is the range of the input pk-pk.
Which one should i use for SQNR?
--- Updated ---

OK if i understand it correcty we take an amplitude which could fit our FSR of the DAC.
so if my DAC ranges 0-1 then sinus that can fit this is 0.5+0.5sint(wt)
So in SQNR We use the amplitude of the sinus
but my LSB has nothing to do with the input its stricktly ADC parameter VFS/2^B
Correct?
Thanks.
 
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Yes, the amplitude is 0.5 and the signal power is 0.5^2/2. The ADC converts that sine wave with some error introduced in every sample - the quantization error. For convenience we think of the error as being uniformly distributed in the range of +/- LSB/2. The power of the error is LSB^2/12. We want to compare the power of the signal that we want to the power of the error that we don't want. That is SQNR.
 
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