# Pulse-Amplitude Modulation minimum clock frequency

#### skyline977

Joined Jan 14, 2021
29
Hi,
Below is the question and answer:

Source:
Study Guide for Fundamentals of Engineering (FE) Electrical & Computer CBT Exam- Third Edition By Wasim Asghar, ISBN:9798670880909

However, as per the below book it's given as :

Source:
FE Reference Handbook 10.0.1, by NCEES, ISBN 978-1-947801-11-0

It clearly says that the signal can be generated by the sampling frequency i.e. the correct answer is 15 kHz.
Am I right?

#### crutschow

Joined Mar 14, 2008
34,669
It clearly says that the signal can be generated by the sampling frequency i.e. the correct answer is 15 kHz.
Am I right?
No.

Where does it "clearly" state that?

A 15KHz sine wave has two peaks per cycle, so how could you reproduce that with only one sample per cycle?

#### Deleted member 115935

Joined Dec 31, 1969
0
Hi,
Below is the question and answer:
View attachment 228565
Source:
Study Guide for Fundamentals of Engineering (FE) Electrical & Computer CBT Exam- Third Edition By Wasim Asghar, ISBN:9798670880909

However, as per the below book it's given as :
View attachment 228566
Source:
FE Reference Handbook 10.0.1, by NCEES, ISBN 978-1-947801-11-0

It clearly says that the signal can be generated by the sampling frequency i.e. the correct answer is 15 kHz.
Am I right?
As highlighted by @crutschow

The main thing to consider here, is the nyquest theory,

If you think of a sine wave of 15 Khz,
then to have at least one sample on the +ve and the -ve part of the waveform, then the minimum is two samples per cycle,
i.e 30 KHz.

This works for sampling and generating,

Try drawing a sine wave with less than 2 samples per period.

Now in practise you would have many more samples per cycle,

Yes a PAM can be made by taking samples at a frequency of a signal,
but that sampling frequency has to as a minimum meet Nyquest.