common terminology of logic gates
TRANSCRIPT
Common terminology of logic gates
Logic gate : An electronic circuit with a single output and one or more inputs .
Truth table : A table that summarises all the possible input and output of a logic gate.
Boolean algebraic: A form of symbolic logic which provides a mathematical procedure for manipulating logical relationships in symbolic form.
Number of possibilities inputs and outputs..
N = 2n N = number of outputs n = number of inputs
Types of logic gates
There are seven types of logic gates:(a) NOT gate(b) AND gate(c) OR gate(d) NAND gate(e) NOR gate
NOT gate
The symbol of for a NOT gate is:
The Boolean algebraic is:
The truth table is:
Input OutputA X0 11 0
An equivalent circuit to a NOT gate:
Input Output
A XSwitch off Lights upSwitch on Goes off
AND gate
The symbol of for an AND gate is:
LESSON 4Analysing logic gates
The Boolean algebraic is:
The truth table is:
Input OutputA B X0 0 00 1 01 0 01 1 1
An equivalent circuit to an AND gate:
Input OutputA B X
Switch off Switch off Goes offSwitch off Switch on Goes offSwitch on Switch off Goes offSwitch on Switch on Lights up
OR gate
The symbol of for an OR gate is:
The Boolean algebraic is:
The truth table is:
Input OutputA B X0 0 00 1 11 0 11 1 1
An equivalent circuit to an OR gate:
Input OutputA B X
Switch off Switch off Goes offSwitch off Switch on Lights upSwitch on Switch off Lights upSwitch on Switch on Lights up
NAND gate
The symbol of for an NAND gate is:
The Boolean algebraic is:
The truth table is:
Input OutputA B X0 0 10 1 11 0 11 1 0
NOR gate
The symbol of for an NOR gate is:
The Boolean algebraic is:
The truth table is:
Input OutputA B X0 0 10 1 01 0 01 1 0
Example 1
The figure shows a logic gate with inputs P and Q.
If the input P = 0011010 and the input S = 1100011 , what is the output X?
Solution
Example 2
The diagram shows two signals are connected to the inputs A and B of an OR gate.
Draw the output signal X.
Solution
Example 3
Work out the truth for the combination of logic gates in figure below.
Solution
Applications of Logic Gates in Control Systems
(1) Automatic Fan for cooling system
LightDetector
TemperatureDetector
Fan
0 0 00 1 01 0 01 1 1
(2) Fire Alarm system
SmokeDetector
HeatDetector
Siren
0 0 Not activated0 1 Activated1 0 Activated1 1 Activated
(3) Fire Control system
Input OutputSmoke Heat Fire Fire
detector detector extinguisher Alarm0 0 0 00 1 0 11 0 0 11 1 1 1
(4) Automatic Heater
Input OutputSwitch Temperature
detectorLight detector
0 0 0 11 0 0 00 0 1 01 0 1 10 1 0 01 1 0 10 1 1 01 1 1 1
(5) Control system for street lights
Input OutputSwitch Light sensor Street light
0 0 10 1 01 0 11 1 1