Page 300 - FUNDAMENTALS OF COMPUTER
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300 Fundamentals of Computers NPP
The circuit shown in the dotted box can be ~m°Šg _| Omo n[anW ~Zm`m J`m h¡ Cgo EH$ hr JoQ>
considered as a single gate whose inputs are A _mZm Om gH$Vm h¡ {Og_| A VWm B BZnwQ> XoZo na
and B, and the output is A+ B . This Gate is AmCQ>nwQ> A+ {_boŸ& BgH$m Zm_ NOR JoQ> Bg
B
called NOR gate due to following equation:
àH$ma go n‹S>m …
NOT + OR = NOR
The symbol for NOR gate can be drawn as: NOR JoQ> H$m g§Ho$V Bg Vah go ~Zm`m Om
gH$Vm h¡…
A
A+B
B
The small circle at the output side called a AmCQ>nwQ> _| Omo N>moQ>m-gm d¥Îm h¡, dh NOT {H«$`m
bubble, shows NOT operation. The truth table H$mo Xem©Vm h¡Ÿ& Xmo-BZnwQ>m| dmbo NOR JoQ> H$s gË`-
for two-input NOR Gate can be drawn as : Vm{bH$m H$mo Bg Vah go ~Zm`m Om gH$Vm h¡Ÿ:
A B Y=A+B
0 0 1
0 1 0
1 0 0
1 1 0
The truth table shows that the output of gË`-Vm{bH$m go ñnîQ> h¡ {H$ NOR JoQ> H$m
NOR gate is 1, only when all the inputs are AmCQ>nwQ> 1 V^r hmoJm O~ BgHo$ gmao BZnwQ> eyÝ` hm|JoŸ&
Zero. The NOR gate is also a binary gate, NOR JoQ> Ho$ ^r H$_ go H$_ Xmo BZnwQ> hmoZm Oê$ar h¡,
because it must have atleast two inputs. The Bgr{bE Bgo ~mBZar JoQ> H$hVo h¢Ÿ& VrZ BZnwQ>m| dmbo
symbol and expression for 3-input NOR gate NOR JoQ> H$m g§Ho$V d ì`§OH$ Bg àH$ma go {bIm Om
are shown below :
gH$Vm h¡ …
A
B
C Y = A+B+C
XOR Gate (Exclusive OR Gate) EŠñŠcy{Od OR JoQ>
In XOR Gate the output is one when `h dh JoQ> hmoVm h¡ {OgHo$ BZnwQ> _| `{X 1 H$s
number of ones in the input side is odd. And g§»`m {df_ h¡ Vmo AmCQ>nwQ> 1 hmoVm h¡ AÝ`Wm 0 hmoVm
the output is Zero when number of ones is
even. Using this property we can draw the h¡Ÿ& Bgr Ho$ AmYma na XOR JoQ> H$s gË`-Vm{bH$m ~ZmB©
truth table for 2-input X-OR gate. The symbol Om gH$Vr h¡ …
of XOR gate is also shown below :
