Noise margin is a parameter closely related to the input-output voltage characteristics. This parameter allows us to determine the allowable noise voltage on the input of a gate so that the output will not be affected. The specification most commonly
used to specify noise margin (or noise immunity) is in terms of two parameters- The LOW noise margin, NML, and the HIGH noised margin, NMH. With reference to Fig 4. NML is defined as the difference in magnitude between the maximum LOW output
voltage of the driving gate and the maximum input LOW voltage recognized by the driven gate. Thus,
The value of NMH is difference in magnitude between the minimum HIHG output voltage
of the driving gate and the minimum input HIGH voltage recognized by the receiving
gate. Thus,
Where,
VIHmin = minimum HIGH input voltage VILmax = maximum LOW input voltage VOHmin= minimum HIGH output voltage VOLmax= maximum LOW output voltage.
