Page 290 - FUNDAMENTALS OF COMPUTER

NPP

290 Fundamentals of Computers NPP

AND Gate AND JoQ>
AND Gate is a type of logic gate in which Bg àH$ma Ho$ JoQ> _| AmCQ>nwQ> 1 V^r hmoVm h¡ O~
output is 1 only when all the inputs are 1. In gmao BZnwQ> 1 hmoŸ& AWm©V² EH$ ^r BZnwQ> 0 hmo OmVm h¡
other words the output of AND gate is 0 when
any of the inputs is 0. This gate must have at Vmo AmCQ>nwQ> 0 hmo OmVm h¡Ÿ& Bg JoQ> _| H$_ go H$_ Xmo
least two inputs. Therefore this gate is called BZnwQ> hmoZm Oê$ar h¡Ÿ& Bg{bE Bgo ~mBZar JoQ> H$hVo h¢Ÿ&
binary gate. The symbol for AND gate is similar BgH$m g§Ho$V A§J«oOr Ho$ Aja ‘D’ Ho$ g_mZ hmoVm h¡Ÿ& BgHo$
to English letter ‘D’. The left side of the symbol
will show input signals and the right side will ~mE± BZnwQ> Xem©Vo h¢ VWm XmE± AmCQ>nwQ> H$mo Xem©Vo h¢Ÿ&
show output signal. Suppose A and B are two `{X A VWm B BZnwQ> hmo VWm Y AmCQ>nwQ> hmo Vmo EÊS> JoQ>
input signals and Y is output. The symbol can Ho$ g§Ho$V H$mo Bg Vah ~Zm`m Om gH$Vm h¡ …
be drawn as below:

A
Y = A.B
B

The output expression for AND Gate is: EÊS> JoQ> Ho$ {bE AmCQ>nwQ> H$m ì`§OH$ Bg àH$ma
go ~Zm`m Om gH$Vm h¡…
Y = A.B
It shows that Y is 1 only when A and B both Bggo `h àVrV hmoVm h¡ {H$ Y V^r 1 hmoJm O~ A
are 1. If any of these is Zero, Y is Zero. On the VWm B XmoZm| 1 hmoŸ& `{X EH$ ^r BZnwQ> 0 hmo Vmo AmCQ>nwQ>
basis of this fact we can draw truth table 0 hmo OmEJmŸ& BgHo$ AmYma na h_ AND JoQ> H$s gË`
between A, B and Y:
Vm{bH$m ~Zm gH$Vo h¢, Omo {H$ ZrMo Xem©`r JB© h¡…
Truth table for 2-input AND Gate
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
The same concept may be extended to more Bgr àH$ma h_ EH$ Eogm AND JoQ> ^r ~Zm gH$Vo
than two inputs. The output is 1 only when all h¢ {Og_| Xmo go A{YH$ BZnwQ> hmoŸ& O¡go 3- BZnwQ> dmbo
the inputs are 1. The symbol for 3-input AND
gate can be drawn as: AND JoQ> H$m g§Ho$V d g_rH$aU ZrMo ~Vm`m J`m h¡Ÿ:

A
B Y = A.B.C
C