digital electronics introduction

8/16/2019 Digital Electronics Introduction

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DIGITAL ELECTRONICS


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Introduction to Digital Electronics

Digital Electronics represents information (0, 1) with onlytwo discrete values.

Ideally

“no voltage (e.g., 0v) represents a 0 and

“full source voltage (e.g., !v) represents a 1"ealistically

“low voltage (e.g., #1v) represents a 0 and

“high voltage (e.g., $%v) represents a 1


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What is a Digital System?Digital system&ystem that ta'es in digital inputs and generates digital

outputsEample *omputer

Digital inputs (letters and num+ers from 'ey+oard)Digital output (new num+ers or letters stored to a file or display

on screen)

any other digital systems eist*ell phones, automo+ile control engines, - set top +oes,

musical instruments, DD players, digital cameras, finger printrecognition, …


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Analog versus Digital

/nalog systems process timevarying signals that canta'e on any value across a continuous range of voltages

(in electricalelectronics systems).

Digital systems process timevarying signals that can

ta'e on only one of two discrete values of voltages (inelectricalelectronics systems).Discrete values are called 1 and 0 (23 and 244, 5I65

and 728, -"9E and 4/7&E, etc.)


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Digital vs. Analog

Digital signalDiscrete

&ignal that can have one of a finite set of possi+le values

/nalog signal*ontinuous

&ignal that can have one of an infinite num+er of

possi+le values


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Analog versus Digital

A digital signal,unlike continuousanalogue signal,varies abrutl! andc"anges bet#eendistinct voltage orcurrent levels$

%co&&onl! t"e ' or (voltage levels o) abinar! s!ste&*

analoguesignal

digital signal


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Binary Digits and Logic Levels

Digital electronics uses circuits thathave two states, which are represented

+y two different voltage levels called

5I65 and 728. -he voltagesrepresent num+ers in the +inary system

In +inary, a single num+er is called abit (for binary digit ). / +it can have thevalue of either a 0 or a 1, depending onif the voltage is 5I65 or 728

5I65

728

V 5(ma)

V 5(min)

V 7(ma)

V 7(min)

Invalid


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Digital WaveformsDigital waveforms change +etween the 728 and 5I65

levels. / positive going pulse is one that goes from a

normally 728 logic level to a 5I65 level and then +ac'

again. Digital waveforms are made up of a series of

pulses

4alling or

leading edge

(+) 3egative:going pulse

5I65

"ising or

trailing edge

728

(a) ;ositive:going pulse

5I65

"ising or

leading edge

4alling or

trailing edge

728t 0

t 1

t 0

t 1


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Advantages of Digital Systems

1. Digital systems are generally easier to design

. ore digital circuitry can +e fa+ricated on I* chips


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Limitation of Digital Systems

Digital signal will not +e an eact copy of the original

analogue signal sampling error

-o ta'e advantages of digital techni?ues*onvert analog inputs to digital

;rocess the digital

*onvert the digital outputs to analog

@oth analog and digital techni?ue can +e employed inthe same system called hybrid system


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Integrated Circuits

I* is an electronic circuit, *onstructed entirely on a single piece of semiconductor material called su+strate ,referred

as a chip.

*lassification of I* /nalog A Digital

Digital IC are collection of resistors, diodes and transistorfa+ricated on a single chip.

3o additional component re?uired for their operation.

2; : logic level 0 or 1.

7ow cost ,low power, smaller siBe./nalog I*s, such as sensors and operational amplifier,

wor' +y processing continuous signals


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+reared b! $T$ NG(-

Integrated Circuits

/ gate is a physical implementation of a @ooleanfunction

7ogic gates are usually em+edded in Integrated*ircuits I*s, sometimes referred as *hips

/ccording to its compleity, I*s are classified as&&I, &I, 7&I and 7&I ( small, medium, l arge Avery l arge scale integration)

7ogic gates I*s may +e *2& type, +oth re?uirea power supply of C! volts and a ground in

addition to the logic inputs DI; type (dualinline pac'age) logic I*s will +eused in our eperiments

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Top view of a logic gate IC


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Levels of Integration

Digital I* are *ategoriBed according to their circuit

*ompleity.num+er of e?uivalent logic gates on thesu+strate.

&mall &cale Integration or (&&I) *ontain up to 10

transistors or a few gates within a single pac'age such as

/3D, 2", 32- gates.edium &cale Integration or (&I) +etween 10 and 100

transistors or tens of gates within a single pac'age and

perform digital operations such as adders, decoders,

counters, flipflops and multipleers.

7arge &cale Integration or (7&I) +etween 100 and 1,000

transistors or hundreds of gates and perform specific digital

operations such as I2 chips, memory, arithmetic and logic

units.


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Levels of Integration contd..!

ery7arge &cale Integration or (7&I) +etween 1,000 and10,000 transistors or thousands of gates and perform

computational operations such as processors, large memory

arrays and programma+le logic devices.

&uper7arge &cale Integration or (&7&I) +etween 10,000and 100,000 transistors within a single pac'age and perform

computational operations such as microprocessor chips,

microcontrollers, +asic ;I*s and calculators.

9ltra7arge &cale Integration or (97&I) more than 1million transistors the +ig +oys that are used in computers

*;9s, 6;9s, video processors, microcontrollers, 4;6/s

and comple ;I*s.

digital electronics introduction

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