MUX Help!

[watzmann]

Hi All ,

i'm trying a circuit using 74151 Multipliexer , on protous , actaully i have a problem,

when i try to simulate it , nevertheless the ABC selection i select the output is same , no differance ,

i think the enable port have to be connected to the Ground , and i did that , but no way the output doesn't change when i change the switch case.

here is the schematic , and please tell me what's wrong , i have just deleted the E port wiring ,

thank you

 

[on1aag]

Hi Watzmann,

You shouldn't have left the unused inputs floating.
If you want them to be at logical zero you have to connect
them to gnd, when using TTL an open input is regarded as
a logical one.
Connect the three used inputs to gnd and leave the other's
open, however this is not good design practice, all unused
inputs should be connected to either to a logical zero or a
logical one.

on1aag.

 

[watzmann]

yes it works fine now , thank you ,

i'm planning to use NE555 to afford the logic signal