Page 293 - FUNDAMENTALS OF COMPUTER

NPP

NPP Number System, Boolean Algebra and Logic Circuits 293

D 1

A

D
2
B

D 3

C Y

R
L

+ 5V
OR Gate OR JoQ>
In this logic gate, the output is 1 when any Bg JoQ> _| EH$ ^r BZnwQ> `{X 1 hmo OmVm h¡ Vmo
of the inputs is 1. In other words the output of AmCQ>nwQ> 1 hmoJmŸ& Xygao eãXm| _| AmCQ>nwQ> eyÝ` V^r hmoJm
this gate is Zero only when all the inputs are Zero.
This gate must have at least two inputs OR gate can O~ gmao BZnwQ> eyÝ` hmoŸ& OR JoQ> _| H$_ go H$_ Xmo BZnwQ>
be drawn as: hmoZm Amdí`H$ h¡Ÿ& BgH$m g§Ho$V Ed§ AmCQ>nwQ> H$m
g_rH$aU Bg àH$ma go {bIm Om gH$Vm h¡…

A

A + B
B

The expression for output of OR Gate is AmCQ>nwQ> H$m ì`§OH$ A + B h¡Ÿ& `hm± na ‘+’ H$m
A+B. Here ‘+’ is used as an ‘OR-operator’ not Cn`moJ ‘OR {H«$`m’ H$mo Xem©Zo Ho$ {bE {H$`m J`m h¡ Z {H$
as an addition operator. Therefore A+B is called ‘Omo‹S>’ Ho$ {bEŸ& {\$a ^r Bgo A VWm B H$m ‘Vm{H©$H$ `moJ’
logical sum of A and B. The truth table for 2-
input OR gate in accordance with its defini- H$hVo h¢Ÿ& Bg JoQ> H$s gË` Vm{bH$m, BgH$s n[a^mfm Ho$
tion can be drawn as: AZwgma Bg àH$ma ~ZmB© Om gH$Vr h¡…