Basic electronic circuits input voltage

[KhaledOsmani]

Hello,
Some of the basic electronic circuits, mainly consisting of 555 timer & CD4017 and also other ICs have a range of input voltages such as the circuit could function from 6V to 9V for example.


How could this be justified and explained?

 

[Gorgon]

You could start looking at the ICs datasheets, where the input requirements for the different voltage levels are defined.