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roam
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Homework Statement
I need some help with the following problem (from an old exam):
A 16-bit single-ramp ADC has a sampling interval of T=1 μs and an input voltage range of 0 to 10V.
Since for this ADC the input must be positive, its design includes a fixed DC input of 5 V upon which the varying signal is superimposed (the 5V DC is not part of the signal). If the varying signal is a sinusoidal voltage of amplitude 1.8V, what is the SNR in dB?
Homework Equations
Signal to noise ratio in dB is given by:
##|(SNR)|_{dB} = 7.8+6b+20 \log(\frac{A}{R})##
R is the range, A is the amplitude, b is the bits.
The Attempt at a Solution
Using the above equation I got
##|(SNR)|_{dB} = 7.8+6\times 16 +20 \log(\frac{1.8}{10}) =88.90 \ dB##
But my answer was marked as incorrect! I'm very confused here.
So, do I need to add the 5V fixed DC to the 1.8V amplitude? But the question clearly states "the 5V DC is not part of the signal".
If I add 5V I will get:
##|(SNR)|_{dB} = 7.8+6\times 16 +20 \log(\frac{6.8}{10}) =100.45 \ dB##
But which method is correct?
Any help is greatly appreciated.