Question

Here, we need to note the specifications for an ADC converter for a phone answering machine that will store audio (phone) messages in digital form and then play them via a DAC. Note that a phone doesn't carry information above 3kHz, so the amplitude accuracy doesn't have to be fantastic.

(a) If we want to resolve the signal to ±0.5% of the full scale of amplitude, how many bits do we need?

(b) What sampling rate would be ideal? (This is assuming that the output filter that smoothens the retrieved analog signal can reduce the amplitude by a factor of at least 200 for frequencies that are 20% above the cutoff frequency, f_3DB ). Explain why.

Answer 1