anlog to digital question, need quick help

[KUMARA SHP]

2. You are designing an electroencephalography (EEG) system, knowing that
the largest expected frequency of the signal is about 120 Hz. What sampling
frequency would you choose, and why? What would be the cut-‐off frequency
for your filter?

3. You have acquired 10,000 samples of an ECG signal sampled at 300 Hz, and
are performing an FFT. What is your frequency step? Which samples
correspond to the frequency range 10-‐20 Hz?

4.You are designing an EEG system, and have selected an A/D converter with
range -‐5/5 V, 12 bits and fs=400 Hz. If your input signal varies from -‐10 to
+10 mV, what amplification factor would you choose and why?

I know the answer for Q2 , BUT i DONT KNOW CUT OFF FREQUENCY
PLEASE GIVE ME ANSWERS QUICKLY

 

[Harald Kapp]

What is your answer to Q2?

Sampling frequency as well as cut-off frequency of the filter not only depend on the Nyquist-Shannon sampling theorem but also on the characteristics of your filter. A steep filter's (filter order higher than 1) cut-off frequency can be much closer to the sampling frequency than the cut-off frequency of a filter with a slowly falling slope (first order filter).