Page 297 - FUNDAMENTALS OF COMPUTER

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NPP Number System, Boolean Algebra and Logic Circuits 297

A Y = A
The single possible truth table for NOT NOT JoQ> hoVw {g\©$ EH$ hr gË` Vm{bH$m ~ZoJr…
gate can be drawn as:

Input Output
A Y=A
0 1
1 0

In electronic circuits, NOT gate is used to BboŠQ´>m°{ZH$ n[anW _| NOT JoQ> H$m Cn`moJ dmoëQ>oO
invert the level of the signal. When the input is Ho$ ñVa H$mo CbQ>Zo Ho$ {bE {H$`m OmVm h¡Ÿ& O~ BZnwQ>
high voltage, the output is low voltage and na CÀM dmoëQ>oO XoVo h¢ Vmo AmCQ>nwQ> na {ZåZ dmoëQ>oO
vice-versa. Therefore it is called Inverter. àmßV hmoVm h¡Ÿ& Bg{cE Bgo BÝdQ>©a ^r H$hVo h¢Ÿ&

NOT Gate Using a Switch pñdM H$m Cn`moJ H$aHo$ NOT JoQ> ~ZmZm

R

A
Switch Y
+5v
Bulb

Consider the above circuit. When the Cnamoº$ n[anW H$mo XoImoŸ& O~ pñdM Iwbm hmoJm (A
switch is open (A = 0), the bulb will glow, = 0) Vmo ~ë~ _| ~oQ>ar go grYr Ymam ~ë~ _| ~hoJr VWm
because it will receive current from the battery. Y = 1 {_boJmŸ& bo{H$Z O~ pñdM H$mo ON H$a|Jo Vmo gmar
But when the switch is closed (A = 1), the whole
current will be drawn by the switch because of Ymam pñdM _| go hmoH$a OmEJrŸ Š`m|{H$ pñdM H$m à{VamoY
its negligible resistance. Therefore bulb will ZJÊ` hmoVm h¡Ÿ& ~ë~ _| go H$moB© Ymam àdm{hV Zht hmoJrŸ&
not glow (Y = 0). Therefore the circuit follows AWm©V² EH$ pñdM H$m `h n[anW NOT JoQ> H$s gË`-
the truth table of NOT Gate (Invertor). Vm{bH$m H$m nmbZ H$aVm h¡Ÿ&

NOT Gate Using Transistor Q´>m§{OñQ>a H$s ghm`Vm go NOT JoQ> ~ZmZm
A transistor can be used to design a NOT EH$ NPN Q´>m§{OñQ>a H$s ghm`Vm go NOT JoQ> ~Zm
gate. Consider the following circuit: gH$Vo h¢ …