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DIGITAL SIGNAL PROCESSING (DSP) 199
2 Signal-to-Noise Ratio = 40 db
1
0
-1
-2

Signal-to-Noise Ratio = 20 db
2
1
0
-1
-2

Signal-to-Noise Ratio = 6 db
2
1
0
-1
-2

Signal-to-Noise Ratio = 0 db

2
1
0
-1
-2

FIGURE 8-5 A visual look at S/N ratios

ber, there’s no sense trying for more. In general, use an A/D that’s just somewhat better
than the signals it must measure.
So here’s our first pop quiz! If the signals have an S/N ratio of 60 db, how many bits
of resolution should the A/D have?