> able to detect voltages close to 5volts and 0volts as I know of no 
> opamp that can swing to their rail voltages.. even those rail-rail 
> opamps cant do that..

Some r-r opamps have inbuilt power supply inverters to give them 
internal rails greater than rail so they can do the impossible.  You 
can often do the same yourself if you don't mind being naughty or 
clever by having some dropping resistance in the supply or using 
voltage upstream of the regulator. Applicability varies with 
application.


        Russell 

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