AND GAte problem

Thread Starter

Hassaan Aslam

Joined Apr 20, 2013
11
hi!!! i am a beginner, when i use and gate i get '1' output even if my inputs are '0'. i have tried two ic's 7408 and 4081 but i am getting same problem with both of them. can any one guide me hoe to use these ic's correctly.... :confused: :( :confused:
 
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kubeek

Joined Sep 20, 2005
5,587
did you connect the inputs to ground, or are you simply assuming that unconnected means logic 0?
 

DerStrom8

Joined Feb 20, 2011
2,373
Another question is what are you using for power? The 7408 is only designed for 5 volts on Vcc. If you connected a higher voltage, you've likely damaged the chip.

Also, what are you using to drive the inputs?
 

Thread Starter

Hassaan Aslam

Joined Apr 20, 2013
11
i am currently using 4081 i am using 5 volt input but i have not connected inputs to ground.
 

Thread Starter

Hassaan Aslam

Joined Apr 20, 2013
11
if the inputs are connected to ground then how will i apply "1" inputs to the input terminals???
 

kubeek

Joined Sep 20, 2005
5,587
You need to have ALL inputs connected to either supply voltage or ground or output of another gate. Without that the inputs will act like antenna and will have any value.
 

kubeek

Joined Sep 20, 2005
5,587
You connect them to either ground of supply voltage. You can also connect them through a resistor to ground, for example 10k.
 

Ramussons

Joined May 3, 2013
794
I would Never, Never design a circuit without following this fundamental rule!

Ramesh
 
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