The document discusses the differences between analog and digital signals, highlighting their definitions, characteristics, advantages, and disadvantages. Analog signals are continuous and can represent an infinite range of values, while digital signals are discrete with a finite number of possible values, making them easier to process but less precise. It also explains the processes of analog-to-digital and digital-to-analog conversion, along with various types of converters used in signal processing.

1. ADC &DAC
Ishraq Madi Jboor
Noor Al_huda Mahir

2. An analog signal is a continuous signal that contains time-varying quantities,
such as temperature or speed, with infinite possible values in between
An analog signal can be used to measure changes in some physical phenomena
such as light, sound, pressure, or temperature.
Sine Wave Random- Periodic
Analog :-

3. Analog Signals
 Continuous
 Infinite range of values
 More exact values, but more
difficult to work with
Digital Signals
 Discrete
 Finite range of values
 Not as exact as analog, but easier
to work with
Example:
A digital thermostat in a room displays a
temperature of 72. An analog thermometer
measures the room temperature at 72.482.
The analog value is continuous and more
accurate, but the digital value is more than
adequate for the application and significantly
easier to process electronically.

4. Advantages:
1-Major advantages of the analog signal is
infinite amount of data.
2-Density is much higher.
3-Easy processing.
Disadvantages:
1-Unwanted noise in recording.
2-If we transmit data at long distance then unwanted disturbance is
there.
3-Generation loss is also a big con of analog signals.

5. Is a type of signal that can take on a set of discrete values (a quantized signal)
Digital signals can represent a discrete set of values using any discrete set
of waveforms .. And we can represent it like (0 or 1) ,( on or off )….. etc
Digital -:

6. Digital signals can be optical, electrical, acoustic, or others. Digital signals are
present in all digital electronics, notably computing equipment and
telecommunications.
Digital signals must have a finite set of possible values. The number of values in the
set can be anywhere between two and a-very-large-number-that’s-not-infinity. Most
commonly digital signals will be one of two values – like either 0V or 5V. Timing
graphs of these signals look like square waves

7. Or a digital signal might be a discrete representation of an analog waveform. Viewed
from afar, the wave function below may seem smooth and analog, but when you look
closely there are tiny discrete steps as the signal tries to approximate values.

8. • That’s the big difference between analog and digital waves. Analog waves are
smooth and continuous, digital waves are stepping, square, and discrete.
• Working with electronics means dealing with both analog and digital signals,
inputs and outputs. Our electronics projects have to interact with the real,
analog world in some way, but most of our microprocessors, computers, and
logic units are purely digital components. These two types of signals are like
different electronic languages; some electronics components are bi-lingual,
others can only understand and speak one of the two.

9. • Quantizing - breaking down analog value is a set of finite states
• Encoding - assigning a digital word or number to each state and matching
it to the input signal
ADC
The number of possible states that the converter can output is: N=2n
(Where n is the number of bits in the AD converter)
Analog quantization size:
Q= (V max -V min)/N
Quantizing -:
There are two step Process -:

10. Example: For a 3 bit A/D converter, you have 0-10V signals. Separate them into
a set of discrete states
Sol:
N=23=8
Q= (10V – 0V)/8 = 1.25V
Quantization
Output States Discrete Voltage Ranges (V)
0 0.00-1.25
1 1.25-2.50
2 2.50-3.75
3 3.75-5.00
4 5.00-6.25
5 6.25-7.50
6 7.50-8.75
7 8.75-10.0

11. Encoding
Output States Output Binary Equivalent
0 000
1 001
2 010
3 011
4 100
5 101
6 110
7 111
Here we assign the digital value
(binary number) to each state for
the computer to read.

12. • It is a process of taking a sufficient number of discrete values at point on a
waveform that will define the shape of waveform.
• The more samples you take, the more accurately you will define the waveform.
• It converts analog signal into series of impulses, each representing amplitude of
the signal at given point…….
• Flash ADC
• Digital-Ramp/Dual slope/Counter slope ADC
• Successive Approximation ADC
Sampling -:
Types of A/D convertor :-

13. Consists of a series of comparators, each one comparing the input signal to a
unique reference voltage. The comparator outputs connect to the inputs of a
priority encoder circuit, which produces a binary output
3 bit Flash ADC Circuit
Flash ADC :-

14. • Simplest in terms of operational theory
• Most efficient in terms of speed, very fast
• Limited only in terms of comparator and gate propagation delays
• Lower resolution
• Expensive
• For each additional output bit, the number of comparators is doubled
Advantages :-
Disadvantages :-

15. Dual Slope ADC
Also known as Counter-Ramp or Digital Ramp ADC, A dual slope ADC is
commonly used in measurement instruments
Dual Slope ADC circuit

16. Successive approximation ADC
Much faster than the digital ramp ADC because
it uses digital logic to converge on the value
closest to the input voltage.
A comparator and a DAC are used in the process

17. Successive approximation ADC circuit out put

18. ADC Resolution Comparison
0 5 10 15 20 25
Successive Approx
Flash
Dual Slope
Resolution (Bits)
Type Speed (relative) Cost (relative)
Dual Slope Slow Med
Flash Very Fast High
Successive Approx Medium – Fast Low

19. Digital-to-analog conversion is a process in which signals having a two defined levels or
states (digital (binary)) are converted into signals having a theoretically infinite number
of states (analog (current, voltage, or electric charge)). A common example is the
processing, by a modem, of computer data into audio-frequency (AF) tones that can be
transmitted over a twisted pair telephone line. The circuit that performs this function is
a digital-to-analog converter (DAC).
(1-2)
DAC

20. binary weighted resistor DAC :-
• Output of each bit of the register will depend on whether a 1 or a 0 is stored in
that position
• Example ... 0 the output will be 0 volt
1 the output will be 5 volt
• resistance R is inversely proportional to binary weight of each digit

21. Buffering the Resistor :-
all input currents sum at S and go through Rf
(Vo = -If × Rf)
Vo = -If × Rf =-(I1+I2+I3+I4)×Rf

22. Digital/analog example :-
calculate the output voltage for an input code word 0110 if a logic
1 is 10V and logic 0 is 0V
and R = Rf =1k
I=V/R
I1=I4=0
I2=10V/2R = 10/2K= 5 mA
I3=10V/4R=10/4K=0.25 mA
Vo = -If × Rf = -(0.0052) × 1000
= -5.2 volts

23. Basically, digital-to-analog conversion is the opposite of analog-to-digital conversion.
In most cases, if an analog-to-digital converter (ADC) is placed in a communications
circuit after a DAC, the digital signal output is identical to the digital signal input.
Also, in most instances when a DAC is placed after an ADC, the analog signal
output is identical to the analog signal input.

24. Signal transformation life cycle

25. The final step

26. There is a huge deferent between these signals :
Analog Digital
Signal
Analog signal is a
continuous signal which
represents physical
measurements.
Digital signals are discrete
time signals
Waves Denoted by sine waves Denoted by square waves
Representation
Uses continuous range of
values to
represent information
Uses discrete or
discontinuous values to
represent information
Data transmissions
Subjected to deterioration
by noise during
transmission and write/read
cycle.
Can be noise-immune
without deterioration during
transmission and write/read
cycle

27. Memory
Stored in the form of wave
signal
Stored in the form of binary
bit
Response to Noise
More likely to get affected reducing
accuracy
Less affected since noise response are
analog in nature
Flexibility Analog hardware is not flexible.
Digital hardware is flexible in
implementation.
Uses
Can be used in analog devices only.
Best suited for audio and video
transmission.
Best suited for Computing and digital
electronics.
Applications Thermometer PCs, PDAs
Bandwidth
Analog signal processing can be done
in real time and consumes less
bandwidth.
There is no guarantee that digital
signal processing can be done in real
time and consumes more bandwidth
to carry out the same information.

28. Power
Analog instrument draws
large power
Digital instrument draws only
negligible power
Cost Low cost and portable Cost is high and not easily
Impedance Low High order of 100 megaohm
Errors
Analog instruments usually
have a scale which is cramped
at lower end and give
considerable observational
errors.
Digital instruments are free
from observational errors like
parallax and approximation
errors.
Example
Human voice in air, analog
electronic devices.
opticals
Computers, CDs, DVDs, and
other digital electronic
devices.

29. Thanks 4 listening