logic-gates,digital-electronics,ch-3,dld-1, on bio-medical engineering [bme]

7/28/2019 LOGIC-GATES,DIGITAL-ELECTRONICS,CH-3,DLD-1, on bio-medical engineering [BME]

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[DIGITAL-ELECTRONICS IN BIO-

MEDICAL ENGINEERING, CH-3: LOGIC-

GATES ][TEXT-BOOK: INTRODUCTORY-DIGITAL-ELECTRONICS BY NIGEL P.COOK]

6/4/2013

Bio-Medical-Engineering Guide .IncMOHAMMAD-SIKANDAR-KHAN-LODHI

NOTE: ITS MY PERSONAL UNIVERSITY PREPARATIONS NOTES FOR UNDERGRADUATE BIO-

MEDICAL ENGINEERING PROGRAM WHAT I LEARNED IN BETWEEN 2006-TO-2007 IN SIR-SYED

UNIVERSITY OF ENGINEERING AND TECHNOLOGY [SSUET], PAKISTAN KARACHI.

MY BLOG: www.medical-image-processing.blogspot.ca

SIR-SYED UNIVERSITY OF ENGINEERING AND TECHNOLOGY [SSUET]:www.ssuet.edu.pk

NOTE: WELL I AM BUILDING MY PERSONAL NOTES FOR BIO-MEDICAL ENGINEERING COURSES

PREPARATIONS ON PDF FILES SINCE 2008 AND PUBLISHED IT ON MY BLOG , AND I ALSO DISPLAY MY

NOTES IN MY BLOG, BUT THIS CHAPTER I WILL NOT DISPLAY OR PUBLISHED TO PUBLIC ON MY BLOG

AND SCRIBD ACCOUNTS BECAUSE THIS DOCUMENT [ OR MY PERSONAL NOES ] CONTAIN THE FIGURES

[OR COPY-RIGHT MATERIAL] OF THIS CHAPTER FROM DIRECTLY THE TEXT-BOOK DUE TO COPY-RIGHT

LAWS , , I ALWAYS TRY TO BUILD MY NOTES ON PDF DOCUMENTS IN SUCH A WAYS IN WHICH I TRY TO

NOT USED ANY COPY-RIGHT MATERIALSON MY PERSONAL NOTES IN PDF , BUT DUE TO LACK OF

TIMING AND IN ORDER TO QUICKLY COMPLETE MY PREPARATIONS OVER BIO-MEDICAL ENGINEERING

COURSE I TAKE THIS STEPS IN WHICH I AM JUST TRY TO SAVING MY TIME IN AVOIDING TO DRAW THE

PICTURES BY MY HANDS ON A PAPER OR ON THE PRINT WHICH CONSUME A LOT OF TIME , SO I TRY TO

GO FAST AND AT LEAST TOOK FIGURES FROM BOOK DIRECTLY AND PLACED ON MY THIS NOTES, AND

THIS DOCUMENT IS NOT FOR SALE , ITS ONLY FOR HELPING ME TO GET HIGHER MARKS IN THIS COURSE.
http://www.medical-image-processing.blogspot.ca/http://www.medical-image-processing.blogspot.ca/http://www.ssuet.edu.pk/http://www.ssuet.edu.pk/http://www.ssuet.edu.pk/http://www.ssuet.edu.pk/http://www.medical-image-processing.blogspot.ca/


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[DIGITAL-ELECTRONICS IN BIO-MEDICAL ENGINEERING, CH-3:

LOGIC-GATES ]

W W W . M E D I C A L - I M A G E - P R O C E S S I N G . B L O G S P O T . C A B Y

S I K A N D A R - L O D H I Page 2-OF-22

Table of ContentsLOGIC-GATES: ................................................................................................................................................ 3

INTRODUCTION: ............................................................................................................................................ 3

(3-1) HARDWARE FOR BINARY SYSTEMS: .................................................................................................... 4

(3-1-1 ) USING THE DIODE TO CONSTRUCT A LOGIC GATE: ..................................................................... 5

Fig 3-2 the Diode being used in a Digital Electronic Circuit. ................................................................. 6

3-1-2 USING THE TRANSISTOR TO CONSTRUCT A LOGIC GATE: .............................................................. 6

3-2 BASIC LOGIC GATES:- ......................................................................................................................... 7

Fig # 3-4 : The OR-Gate : ...................................................................................................................... 8

Fig # 3-8 The AND Gate : ..................................................................................................................... 10

3-3 INVERTING LOGIC GATES [ NOT, NAND , NOR GATES ]: ...................................................................... 12

3-3-1 THE NOT GATE : ............................................................................................................................. 12

3-3-2 THE NOR GATE: ............................................................................................................................. 14

Fig 3-15 THE NOR Gate : .................................................................................................................... 14

FIG # 3-17 A DATA-SELECTOR/MULTIPLEXER/FREQUENCY SELECTOR CIRCUIT: ................................ 16

3-3-3 : THE NAND GATE: ......................................................................................................................... 16

FIG # 3-18 the NAND Gate: ................................................................................................................ 17

Fig 3-20 [ A Binary to Decimal Decoder circuit using NAND gate ] : ................................................... 17

3-4 EXCLUSIVE-LOGIC-GATES: .................................................................................................................... 18

3-4-1 THE XOR GATE [ ]: .................................................................................................... 18

Example of Odd Number Of 1s :.................................................................................................. 18

Figure 3-21 The Exclusive-OR (XOR) Gate: ......................................................................................... 19

3-4-2 THE XNOR GATE [or EXCLUSIVE-NOR GATE ] ;:- .......................................................................... 19

Fig # 3-23 [ the Exclusive-NOR ( XNOR ) Gate ] ................................................................................... 20

Example of Evan Number of 1s : .................................................................................................... 20

Example # TGS : list the outputs you would expect for all possible inputs to a three input XOR gate ?

................................................................................................................................................................ 21

Fig for example # TGS......................................................................................................................... 21


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LOGIC-GATES ]



Fig # TGS-1 [or Fig # 3-24 ] for example # TGS-1 , a Phase detector circuit using an XOR and XNor

gate :- .................................................................................................................................................. 22

Fig # A1 [ build a circuit which switch between XOR and XNOR gate functions :- ............................. 23

LOGIC-GATES:

INTRODUCTION:

Logic-Gate Circuits: Circuits containing predictable gate functions thateither open or close their outputs.

HARDWARE:A term used to describe the electronic, magnetic andmechanical devices of a digital system.

SOFTWARE:A term used to describe the binary instructions and dataprocessed by digital electronics system hardware.

Within any digital electronic system you will find that diodes and transistorsare used to construct logic gate circuits.

Logic gates are in turn used to construct flip-flop circuits, & flip-flops areused to construct register[example: shift-register],counters,& a variety of

other circuits. These logic gates , therefore, are used as the basic building blocks for all

digital circuits, and their purpose is to control the movement of binary data

& binary instructions.

Logic gates, & all other digital electronic circuits , are often referred to ashardware circuits.

By definition, the hardware of a digital electronic system includes all of theelectronic, magnetic and mechanical devices of a digital system.

In contrast, the software of a digital electronic system includes the binarydata (like pure binary and ASCII codes) and binary instructions that are

processed by the digital electronic system hardware.

To use an analogy, we could say that a compact disk player is hardware,and the music information stored on a compact disk and processed by the

player is software.


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LOGIC-GATES ]



Just as a CD player is useless without CDs , a digital system hardware isuseless without software.

In other words , the information on the CD determines what music isplayed, and similarly the digital software determines the actions of the

digital electronic hardware.

Every digital electronic circuit uses logic-gate circuits to manipulate thecoded pulses of binary language.

These logic gate circuits are constructed using diodes and transistors, andthey are the basic decision-making elements in all digital circuits.

In this chapter we will begin by discussing the evolution of the electronicswitch, and then show how diode and transistor switches are used to

construct these digital logic gate hardware circuits.

(3-1) HARDWARE FOR BINARY SYSTEMS:

Digital circuits are often referred to as switching circuits because theircontrol devices (diode and transistors ) are switched between[ b/w] the

two extremes of ON and OFF.

These digital circuits are also called two-state circuits because their controldevices are driven into one of two states: either into the saturation state{fully ON ) , or at Cut-Off state (Fully OFF ) .

These two modes of operation are used to represent the two binary digitsof 1 and 0.

To develop a digital electronic system that could manipulate binaryinformation, inventors need a two-state electronic switch.

Early machines used mechanical switches and electromechanical relays, torepresent binary data by switching current ON or OFF .

Two-state Circuits: switching circuits that are controlled to be either ON orOFF.

These mechanical devices were eventually replaced by the Vacuum tube,which unlike switches and relays, had the advantage of no moving parts


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LOGIC-GATES ]



The vacuum tube , however, was bulky, fragile, had to warm up andconsumed an enormous amount of power.

Finally, compact and low-power digital electronic circuits an d systembecame a reality with the development of semiconductor diode and

transistors switches, letus see how we can use these semiconductor

switches to construct a logic gate.

(3-1-1 ) USING THE DIODE TO CONSTRUCT A LOGIC GATE:


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Fig 3-2 the Diode being used in a Digital Electronic Circuit.

3-1-2 USING THE TRANSISTOR TO CONSTRUCT A LOGIC GATE:

NOT [ or Inverter ]-gate : A logic gate with only one input and one outputthat will invert the binary input [ ]; .


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3-2 BASIC LOGIC GATES:-

i. The OR-gate:the OR-gate can have the two or more inputs, but will alwayshave a single output. [ or A logic gate that will give a High output if either

of its inputs are high. ]

ii. The AND Gate:A logic gate that will give a High output only if all inputs areHigh [or like the OR-gate, an AND-Gate can have two or more inputs, but

will always have a single output].


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iii. Truth table [Or Function-table }:A table used to show the action of adevice as it reacts to all possible input combinations.

Fig # 3-4 : The OR-Gate :

----------------

x= total number of i/p [inputs] to a logic gate.


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Countmax= maximum count = =total number of counts by a logic gate.

= Total Number of Possible Input combinations .{:. 2is include because we are dealing with a Base-2 number system. }

---------


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LOGIC-GATES ]



Fig # 3-8 The AND Gate :

---------

Example : for a five input AND gate, indicate the range of values within the truth

table.?

Solution:

The Number Of Possible Input Combinations Will be :

[ ];

Where: Number of Inputs are [ x=5 ].

So,

[ ];

For Range Of value :

CountMAX= .

---------finished-here-----------

Example : Referring to the circuit in figure 3-10 (a) , describe what would be

present at the output of AND gate for each of the Control switch positions.?

Solution:


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LOGIC-GATES ]



------finished-here------------

Controlled Switch : An electronically controlled switch.

-------


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LOGIC-GATES ]



3-3 INVERTING LOGIC GATES [ NOT, NAND , NOR GATES ]:

Although the basic OR and AND logic gates can be used to construct manydigital circuits , in some circuits applications other logic operations are

needed.

For this reason , semiconductor manufactures made other logic-gate typesavailable.

In this section, we will examine three inverting-type logic gates, called theNOT-Gate, the NOR gate , and the NAND gate .

We will begin with the NOT or Inverter gate , which was introduced earlier..3-3-1 THE NOT GATE :

The NOT [ or logic Inverter ] gate , is the simplest of all the logic gatesbecause it has only one input and one output.


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LOGIC-GATES ]



-------------------------finished-here-------------

Complement=Opposite.

Bubble [small-circle ]: a small circle symbol used to signify an invert function.

-------------


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LOGIC-GATES ]



3-3-2 THE NOR GATE:

A NotOR gate that will give a Low output if any of its inputs are High [orthe name NORis a combination of the two words NOTand OR, and

is used to describe a type of logic gate that contains an OR gate followed by

a NOT gate , as shown in figure 3-15(a) ].

Fig 3-15 THE NOR Gate :

-------------------


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LOGIC-GATES ]



EXAMPLE : [FREQUENCY -SELECTOR / DATA-SELECTOR / MULTIPLEXER CIRCUIT ]:

Referring to the circuit shown in figure 3-17, find whether the LED will flash at a

rate of 1 Hz or 2 Hz for the inputs and switch position shown ?

Solution:

Answer is given in fig # 3-17 below.


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LOGIC-GATES ]



FIG # 3-17 A DATA-SELECTOR/MULTIPLEXER/FREQUENCY SELECTOR

CIRCUIT:

----finished-here-------------

3-3-3 : THE NAND GATE:

A NOT-AND logic gate circuit that will give a High output if any of its inputsare Low [ like NOR, the name NANDis a combination of the two words

NOTand AND, and it describes another type of logic gate that contains

an AND gate followed by a NOT gate , as shown in fig 3-18(a)].


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LOGIC-GATES ]



FIG # 3-18 the NAND Gate:

--------

EXAMPLE : which of the LEDs in figure 3-20 would turn ON, if the binary inputs

at A and B were both High?

Solution:

Decimal LED # 3 will turn ON when inputs A and B were high .

Fig 3-20 [ A Binary to Decimal Decoder circuit using NAND gate ] :

--------finished-here----


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LOGIC-GATES ]



3-4 EXCLUSIVE-LOGIC-GATES:

In this section , we will discuss the final two logic gate types: the exclusive-OR ( XOR ) gate and Exclusive-NOR (XNOR) gate.

Although these two logic gates are not used as frequently as the five basicOR ,AND , NOT, NOR and NAND gates, their function is ideal in some

circuits applications.

3-4-1 THE XOR GATE [ ]:

EXCLUSIVE-OR Gate [ XOR-Gate ]: A logic gate circuit that will given a Highoutput if any Odd number of binary 1s are applied to the input. [ example

of odd number of 1s is

[ ]]. XOR GATE[ ];

Example of Odd Number Of 1s :

i. 1+0=1s 1+0=1 ; [ Odd number of 1s ].ii. 1+1+1=1s 1+1+1=3 ; [ Odd number of 1s ].

iii. 1+1+1+1+1=1s 1+1+1+1+1=5 ; [ Odd number of 1s ].iv.

1+1+1+1+1+1+1=1s

1+1+1+1+1+1+1=7 ; [ Odd number of 1s ].


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LOGIC-GATES ]



Figure 3-21 The Exclusive-OR (XOR) Gate:

-------------finished-here----------

3-4-2 THE XNOR GATE [or EXCLUSIVE-NOR GATE ] ;:-

The XNOR gate , is simply an XOR gate followed by a NOT gate, as shown infigure 3-23 (a). [ or A Not Exclusive OR gate that will give a High Output if

any even Number of binary 1s are applied to the input. ];

Comparing the XOR gate to the XNOR gate , the XOR gate outputs is onlyhigh when there is an odd number of binary 1s at input , whereas with the

XNOR gate , the output is only high when there is an even number of binary

1s at the inputs.

XNOR GATE[ ];


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LOGIC-GATES ]



Fig # 3-23 [ the Exclusive-NOR ( XNOR ) Gate ]

Example of Evan Number of 1s :

i. 0+0=0s0+0=0 ; [ Even number of 1s ].ii. 1+1=1s1+1=2 ; [ Even number of 1s ].iii. 1+1+1+1=1s1+1+1+1=4 ; [ Even number of 1s ].iv. 1+1+1+1+1+1=1s1+1+1+1+1+1=6 ; [ Even number of 1s ].

------------------finished-here---------


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Example # TGS : list the outputs you would expect for all possible inputs

to a three input XOR gate ?

Solution:

Fig for example # TGS

Key conclusion:the output is only 1 when there is an Odd Number of Binary

1sat the inputs applied .

-------------finishedhere--------

Example # TGS-1 : what will be the X and Y outputs from the circuit in figure of ex

# TGS-1 , if the A and B inputs are either out-of-Phase or in-Phase ?

Solution:


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LOGIC-GATES ]



Fig # TGS-1 [or Fig # 3-24 ] for example # TGS-1 , a Phase detector circuit

using an XOR and XNor gate :-

-----------------finished-here------------


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LOGIC-GATES ]



Fig # A1 [ build a circuit which switch between XOR and XNOR gate

functions :-

---------------finished-here------------

-----------------this Chapter # 3 , on Logic-gates finished-here on Digital-electronics,

in Bio-medical-Engineering under-graduate course-------------

XMOHAMMAD-SIKANDAR-KHAN-LODHI

OWNER-OF-MY-PERSONAL-NOTES Wednesday, June 05, 2013


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logic-gates,digital-electronics,ch-3,dld-1, on bio-medical engineering [bme]

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