It is the amount of power that the digital circuit dissipates. The power dissipated is determined by the average current, that is drawn from the supply voltage.
The average current is the average value of the current at LOW gate output(logic ‘o’) and the current at HIGH gate output(logic ‘1’).
It is an unwanted signal that is superimposed on the normal operating signal. Noise may be due to various factors like operating environment, radiations, stray electrical and magnetic fields.
In digital logic circuits, the binary values 0 and 1 represent the LOW and HIGH voltage levels. Due to the interference of the noises, the voltage levels may increase or decrease. This may lead to the wrong operation of the device.
The noise immunity is the ability of the logic device to tolerate the noise without causing spurious change to the output voltage. Noise margin allows the logic device to function properly within the specified limits.