Explain about the term false path? How it find out in circuit? What the effect of false path in circuit?

By timing all the paths into the circuit the timing analyzer can find out all the critical paths into the circuit. Though, the circuit may have false paths that are the paths within the circuit that are never exercised throughout normal circuit operation for any set of inputs.

A case of a false path is demonstrated in figure above. The path going through the input A of the first MUX by the combinational logic out by the B input of the second MUS is a false path. That path can never be activated since when the A input of the first MUX is activated, in that case Sel line will also choose the A input of the second MUX. STA (i.e., Static Timing Analysis) tools are capable to know simple false paths; nonetheless they are not able to classify all the false paths and sometimes report false paths by critical paths. Removal of false paths creates circuit testable and its timing performance predictable which are sometimes faster.