INTRODUCTION

Question 1

Differentiate between analog and digital

Answer 1

Analog signal is a continuous signal in value and time which represents physical measurements while a digital signal is a signal that represents data as a sequence of discrete values.
Analog signals are fast, economical with low accuracy while for digital signals accuracy is related to cost (number of “bits”)
Analog signals are susceptible to noise & distortion while digital signals are less susceptible to noise

*See notes for diagrammatic representation

Question 2

Describe a digital system and give an example

Answer 2

Digital systems process digital signals which can take only a limited number of values (discrete steps), usually just two values are used: the positive supply voltage (+Vs) and zero volts (0V).
The general purpose digital computer is a best known example of digital system.

Question 3

List some examples of devices contained in digital systems

Answer 3

logic gates, flip-flops, shift registers and counters.

Question 4

What are the disadvantages of digital systems?

Answer 4

 Use more energy than analog circuits to accomplish the same tasks, thus producing more heat as well.

 Digital circuits are often fragile, in that if a single piece of digital data is lost or misinterpreted the meaning of large blocks of related data can completely change.

 Digital computer manipulates discrete elements of information by means of a binary code.

 Quantization error (difference between the analog signal and the closest available digital value at each sampling instant from the A/D converter) during analog signal sampling.

Question 5

Describe information variables in digital systems

Answer 5

The variables take on discrete values.
Two level or binary values are the most prevalent values in digital systems. Binary values are represented by values or ranges of values of physical quantities

Question 6

What are the different ways binary values are represented?

Answer 6

 digits 0 and 1
 words (symbols) False (F) and True (T)
 words (symbols) Low (L) and High (H)
 and words On and Off.

Question 7

Illustrate and briefly describe the following signals over time: digital asynchronous and synchronous

Answer 7

*See notes for diagrams

Question 8

What are the applications of logic circuits

Answer 8

 Computers: The brain, body, and limbs of computer systems – Everything except peripherals

 Embedded Systems: The brains that control the system (e.g. avionics, auto electronics, microwaves, etc.)

 Digital Signal Processing (DSP)- various techniques for improving the accuracy and reliability of digital communications. : E.g. in Cellular phones, Digital TVs,
e.t.c