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24.logic gates
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Author : Khairi
LOGIC GATES
Logicgate
Input
Output
Logic gates are electronic switches with one or more input but only one output
Logic gates are commonly found in computers and other electronic system
Input and output for logic gates only 1 or 0
Author : Khairi
TRUTH TABLE
All inputs and outputs of logic gates can be displayed by using a table
The table is known as truth table
LOGIC GATES
Input Output
A B C X
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NOT GATE
Symbol for NOT GATE
A X
INPUT OUTPUT
A X
1
0
Truth table
0
1
Boolean expression
X = A
Output is opposite to input
LOGIC GATES
Author : Khairi
NOT GATE
A X
INPUT OUTPUT
A X
1
0
Truth table
0
1
Corresponding electric circuit
LOGIC GATES
Symbol for NOT GATE
Author : Khairi
A X
INPUT OUTPUT
A X
1
0
Truth table
0
1
Corresponding electric circuit
LOGIC GATES
Symbol for NOT GATE
NOT GATE
Author : Khairi
AND GATE
Boolean expression
X = A B
INPUT OUTPUT
A B X
0
0
0
1
1 0
1 1
0
0
0
1
A
BX
Corresponding electric circuit
Choose all high
LOGIC GATES
Author : Khairi
Boolean expression
X = A B
INPUT OUTPUT
A B X
0
0
0
1
1 0
1 1
0
0
0
1
A
BX
Corresponding electric circuit
LOGIC GATES
AND GATE
Author : Khairi
AND GATE (3 inputs)
Boolean expression for X
X = A B C
A B C=
A
B X
C
LOGIC GATES
Author : Khairi
Combination of possible inputs
23 = 2 x 2 x 2= 8
A B C=
A
B X
C
LOGIC GATESAND GATE (3 inputs)
Author : Khairi
Truth table
A B C X A B C=0 0 0 00 0 1 00 1 0 01 0 0 01 1 0 01 0 1 00 1 1 01 1 1 1
A B C=A
B XC
LOGIC GATESAND GATE (3 inputs)
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NAND GATE
Boolean expression for X
X A B=
A
BX
LOGIC GATES
Author : Khairi
Combination of possible inputs
22 = 2 x 2 = 4
X A B=A
B
LOGIC GATES
NAND GATE
Author : Khairi
Truth table
A B X A B=
Output for NAND GATE is opposite the output of AND GATE
0 0
X A B=A
B
LOGIC GATES
NAND GATE
Author : Khairi
Truth table
A B X A B=0 0
Input 00 for AND GATE produces 0 outputInverting the output to get the output for AND GATE
10 1
X A B=A
B
LOGIC GATES
NAND GATE
Author : Khairi
Truth table
A B X A B=0 0 10 1 1
X A B=A
B
LOGIC GATES
Input 01 for AND GATE produces 0 outputInverting the output to get the output for AND GATE
NAND GATE
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Truth table
A B X A B=0 0 10 1 11 0 11 1 0
Corresponding electric circuit
X A B=A
B
LOGIC GATES
NAND GATE
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EXERCISE
ABC X
Write the Boolean expression for Xand list down all the possible inputs and outputs for the gate in a truth table
LOGIC GATES
Author : Khairi
ABC X = A B C
INPUT OUTPUTA B X00
00
0 10 1
C0101
1 0 01 0 11 1 01 1 1
11111110
LOGIC GATES
EXERCISE
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OR GATE
AB X
Boolean expression for X
X = A + B
INPUT OUTPUT
A B X
0
0
0
1
1 0
1 1
0
1
1
1
Choose any one high
LOGIC GATES
Author : Khairi
OR GATE
AB X
Boolean expression for X
X = A + B
INPUT OUTPUT
A B X
0
0
0
1
1 0
1 1
0
1
1
1
Corresponding electric circuit
LOGIC GATES
Author : Khairi
AB XC Boolean expression for X
X = A + B + CINPUT OUTPUT
A B X
0
0
0
0
0 1
0 1
C
0
1
0
1
1 0 0
1 0 1
1 1 0
1 1 1
0
1
1
1
1
1
1
1
LOGIC GATESOR GATE
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NOR GATE
Boolean expression for X
X = A + B
AB X
INPUT OUTPUT
A B X
0
0
0
1
1 0
1 1
1
0
0
0
LOGIC GATES
Author : Khairi
EXERCISE
Write Boolean expression for X.List all possible inputs and outputs for the logic gate in a truth table
PQ XR
INPUT OUTPUT
P Q X
0
0
0
0
0 1
0 1
R
0
1
0
1
1 0 0
1 0 1
1 1 0
1 1 1
X = P + Q + R
1
0
0
0
0
0
0
0
LOGIC GATES
Author : Khairi
COMBINATION OF LOGIC GATES
In the electronic circuit,logic gates are combined into variouscombination to produce a desired output
LOGIC GATES
AND
NAND
AND
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LOGIC GATES
COMBINATION OF LOGIC GATES
A
B
C
D
X
What is the Boolean expression for X
A B
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LOGIC GATES
COMBINATION OF LOGIC GATES
A
B
C
D
X
What is the Boolean expression for X
A B
C D
Author : Khairi
LOGIC GATES
COMBINATION OF LOGIC GATES
A
B
C
D
X
What is the Boolean expression for X
A B
C D
A B C D
Author : Khairi
P
QX
Write the Boolean expression for X and state the equivalent basic logic gate.
P + Q
P + Q
PQ X
Equivalent logic gate is NOR GATE
LOGIC GATES
COMBINATION OF LOGIC GATES
Author : Khairi
EXERCISE
PQ
R
S
X
Write the Boolean expression for X
LOGIC GATES
X = P Q R S+ +
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LOGIC GATES
COMBINATION OF LOGIC GATES
1
0
0
1
X
What is the output,X ?
0
1
0
Author : Khairi
EXERCISE
Build a truth table for the combination of logic gates above
LOGIC GATES
A B X
0
0
1
1
0
1
0
1
0
1
0
0
A
B X
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EXERCISE
LOGIC GATES
11
11
X
State the output for X
1
0
0
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LOGIC GATES
EXERCISE
1
1
0
1
X
State the output for X
1
0
1
Author : Khairi
LOGIC GATES
EXERCISE
1
1
0
1
X
State the output for X
1
0
0
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SERIAL INPUT
State the output for X
X1011
1001
LOGIC GATES
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1011
1001
1X
LOGIC GATES
State the output for X
SERIAL INPUT
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1X
1011
1001
0
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
1X
1011
1001
01
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
1X
1011
1001
011
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
1X
1011
1001
011
Output X = 1011
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
State the output for X
1011
1001 X
1
LOGIC GATES
SERIAL INPUT
Author : Khairi
1011
1001 X
10
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
1011
1001 X
100
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
1011
1001 X
1001
Output X = 1001
LOGIC GATES
State the output for X
SERIAL INPUT
Author : Khairi
EXERCISE
LOGIC GATES
1111
1001
1101
0001
X
State the output for X
1111
0001
1111
Author : Khairi
LOGIC GATES
EXERCISE
1111
1001
1101
0001
X
State the output for X
0000
1110
1110
Author : Khairi
LOGIC GATES
EXERCISE
1111
1001
1101
0001
X
State the output for X
0000
1110
0001
Author : Khairi
INPUT FROM TIMING DIAGRAM
LOGIC GATES
1
0
1 1
0 0
The input is 1001
Author : Khairi
X
Draw the output for X on timing diagram
Get the input in binary number
1 0 1
0 0 1
Get the output in binary number
= 101
Draw the timing diagram for output X
LOGIC GATES
INPUT FROM TIMING DIAGRAM
Author : Khairi
INPUT P
INPUT Q
OUTPUT X
If P and Q are the inputs
of AND GATE.Draw the output X
LOGIC GATES
INPUT FROM TIMING DIAGRAM
Author : Khairi
EXERCISE
Draw the output if the inputs are fed to NOR GATE
1 0 1 1 1 0 0
0 0 1 1 0 1 0
0 1 0 0 0 0 1
LOGIC GATES
Author : Khairi
EXERCISE
Draw the output X
LOGIC GATES
X
Author : Khairi
ENRICHMENT PRACTICEENRICHMENT PRACTICE
Light sensor
Body heat sensor
P
QX
Relay switch
Security lamp
Name the logic gate P.
NOT gate
Author : Khairi
ENRICHMENT PRACTICEENRICHMENT PRACTICE
Light sensor
Body heat sensor
P
QX
Relay switch
Security lamp
Q is AND gate.Draw the AND gate by using two switches,batteries and lamp.
Author : Khairi
ENRICHMENT PRACTICEENRICHMENT PRACTICE
Light sensor
Body heat sensor
P
QX
Relay switch
Security lamp
Complete the truth table below for output X.
Input light sensor Input body heat sensor Output X
0
0
1
1
0
1
0
1
0
1
0
0
Author : Khairi
ENRICHMENT PRACTICEENRICHMENT PRACTICE
Light sensor
Body heat sensor
P
QX
Relay switch
Security lamp
State the function of the relay switch in the circuit.
To switch on or off the security lamp.
Author : Khairi
Which of the following truth tables represents output R in the circuit ?
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Which of the following truth tables represents output R in the circuit ?
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
What is the get X which produces the output in the truth table ?
A. AND
B. OR
C. NAND
D. NOR
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Which of the Boolean algebraic expression represents the output Z ?
A. Z = X Y
B. Z = X Y
C. Z = X Y
D. Z = X Y
Both S1 and S2 have to close to produce Z high
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Which of the following output signals is produced by the logic gate circuit ?
A. B. C. D.
0101
1001
1110
0110
1110
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
PAST YEARS QUESTIONPAST YEARS QUESTION
Which truth table is correct ?
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Figure shows two combination of logic gates.
a. Name the logic gate M.
OR gate
b. Complete the truth table for P and Q
S1 S2Output P
0
1
1
0
0
1
0
1
0
S1 S2Output Q
0
1
1
0
0
1
1
1
1
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Figure shows the system used to control the level of pesticide in a bottle
Input S1 and S2 is “0” when they receive a low level of radiation and “1”when they receive a high level of radiation.
a. State the level of the pesticide in the bottle if the input S1 is “0”. Give your reason.
Level of pesticide in the bottle is high because it receives low radiationdue to less penetration of radioactive radiation
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Figure shows the system used to control the level of pesticide in a bottle
Input S1 and S2 is “0” when they receive a low level of radiation and “1”when they receive a high level of radiation.
b. State the level of the pesticide in the bottle if the input S1 is “1”. Give your reason.
Level of pesticide in the bottle is low because it receives high radiationdue to higher penetration of radioactive radiation
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
Figure shows the system used to control the level of pesticide in a bottle
Input S1 and S2 is “0” when they receive a low level of radiation and “1”when they receive a high level of radiation.
c. If the output of logic gate system is “1” when the volume of pesticide accepted and “0” if it is rejected.Which combination of logic gate P or Q is suitable to be used ?Give reason for your answer.
Combination of logic gate P because both S1 and S2 have to be “0” when the volumeis acceptable
PAST YEARS QUESTIONPAST YEARS QUESTION
Author : Khairi
PAST YEARS QUESTIONPAST YEARS QUESTION
output
What is the output ?
![Gates and Logic: From Transistors to Logic Gates and Logic ......Gates and Logic: From Transistors to Logic Gates and Logic Circuits [Weatherspoon, Bala, Bracy, and Sirer] Prof. Hakim](https://img.pdfslide.us/doc/110x75/5fa95cb6eb1af8231472f381/gates-and-logic-from-transistors-to-logic-gates-and-logic-gates-and-logic.jpg)
