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Digital Signal

Chapter 14

by FaaDoOEngineers.com

En gagi n g Peer s, In spir in g Car eer s!

FaaDoOEngineers.com


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Chapter Objectives

Differentiate between analog and digital signals

Describe the positive and negative logic

Describe the application of digital signals

Identify the types of digital integrated circuits

Classify the logic families



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Recall

The base of decimal number system is 10

The base of a hexadecimal number system is 16.

The octal number system uses digits from 0 to 7

BCD stands for Binary Coded Decimal and ASCII code

stands for The American Standard Code for

Information Interchange

ASCII stands for American Standard Code for

Information Interchange

EASCII is of 8 bits



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Analog Signals - I

An analog signal is an AC or DC voltage or currentthat varies smoothly or continuously

Analog signals are more accurate compared to digital

signals, as digital signals are sampled outputs ofanalog signals at specific time intervals whereasanalog signals are continuous in nature

The primary disadvantage of analog signals is thatthese signals are responsible to interference whichcauses noise in the signal leading to data loss anddistortion



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Analog Signals - II

Given below is diagrammatic representation of the

types of analog signals



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Question for GD Time Limit-2mins

Where do we use analog signals?



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Digital signals - I

Digital signals are essentially a series of pulses or

rapidly changing voltage levels that vary in discrete

steps or increments

These are pulses of voltage that usually switchbetween two fixed levels

Digital signals are represented by binary numbers

(0's and 1's) in most of the applications



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Digital signals - II

Digital signals support various data compressionmethods such as audio and video compression.Hence, transmission of digital signals require lessbandwidth compared to analog signals

Data in the form of digital signals can be stored easilyon a variety of less expensive data carriers

Electronic circuits that process digital signals arecalled digital, logic, or pulse circuits



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Digital signals - III

Given below is the diagrammatic representation of

the types of digital signals



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What is the difference between analog and

digital signal?



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Positive and Negative Logic -I

The following are the two basic types of logic level

representations:

Positive Logic - When the more positive of two

voltage levels is assigned to the binary 1 state, it

is referred to as positive logic.

Negative Logic - When the negative or least

positive of two voltage levels is assigned to the

binary 1 state, it is referred to as negative logic.



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Positive and Negative Logic - II

Examples of positive and negative logic are

illustrated in the table below:

Positive Logic Negative Logic

Binary 0 = +0.5V Binary 0 = +3.5V

Binary 1 = +3.5V Binary 1 = +0.5V

Binary 0 = -6.0V Binary 0 = 0.0V

Binary 1 = 0.0V Binary 1 = -6.0V



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Applications of digital signal - I

Digital signals are used in a wide range of

technologies as it supports various data transmission

methods, cost-effective data storage facilities and

other features.

Following are some of the applications of digital

signals:

Audio signal processing



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Applications of digital signal - II

Speech processing

Speech recognition

Speech synthesis

Speech enhancement

Speech coding

Digital image processing

Audio compression



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Applications of digital signal - III

Video compression

Digital communications

Computer animation

RADAR

SONAR



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What are the applications of Digital Signal?



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Digital Integrated Circuits (ICs)

A digital integrated circuit, also called as a chip, is a

small electronic device made out of the

semiconductor material that consists of electronic

components like transistors, logic gates, flip-flops,

multiplexers and other circuits.

They are used for variety of devices including

microprocessor, cellular phone, audio and video

equipments automobiles and many more digital

equipments.



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Types of Digital Integrated Circuits

(ICs) - I

The following are the different types of digital

integrated circuits:

SSI (Small-Scale Integration)

MSI (Medium-Scale Integration)

LSI (Large-Scale Integration)

VLSI (Very Large-Scale Integration)



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Types of Digital Integrated Circuits

(ICs) - II

VVLSI (Very Very Large-Scale Integration)

Wafer-Scale Integration (WSI)

System-on-a-chip (SoC or SOC)

Nanotechnology



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What is the difference between SSI and MSI?



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Logic families - I

Logic families are widely categorized as bipolar and

unipolar logic families

The main elements of bipolar IC are resistors, diodes

and transistor

The following are the two types of bipolar ICs:

Saturated Logic - Transistors in the IC are driven

to saturation

Non-saturated Logic - Transistors are not driven

into saturation



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Logic families - II

The saturated bipolar logic families are resistor-

transistor logic, direct-coupled transistor logic,

integrated-injection logic, diode-transistor logic, high-

threshold logic and transistor-transistor logic

The non-saturated bipolar logic families are Schottky

TTL and Emitter-coupled logic



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Logic families - III

MOS devices are unipolar devices and only

MOSFETs are employed in MOS logic circuits. The

MOS logic families consist of PMOS, NMOS and

CMOS

In PMOS only p-channel MOSFETs are used and in

NMOS only n-channel MOSFETs are used whereas

in CMOS both p-channel and n-channel MOSFETs

are employed and are fabricated on the same silicon

chip



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What is the difference between Saturated and

Non-saturated logic families



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Summary - I

Electronic signals and techniques are of two types:

analog and digital

An analog signal is an AC or DC voltage or current

that varies continuously

Digital signals are a series of rapidly changing

voltage levels that vary in discrete steps



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Summary - II

A positive logic is used when the more positive of two

voltage levels is assigned to the binary 1 state

A negative logic is used when the negative or leastpositive of two voltage levels is assigned to the binary

1 state.



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Summary - III

The various applications of digital signals are audio

signal processing, speech processing, digital image

processing, audio and video compression, digital

communications, computer animation, RADAR and

SONAR

A digital integrated circuit is a small electronic device

that consists of electronic components like

transistors, logic gates, flip-flops, multiplexers, and

other circuits



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Summary - IV

Logic families are categorized into bipolar and

unipolar logic families

Bipolar logic is of two types: Saturated and non-

saturated logic

MOS devices are unipolar devices. The MOS logic

families consist of PMOS, NMOS, and CMOS



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Mind Map

Draw a mind map to summarize this chapter


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