Johnson Noise is a type of electrical noise generated by the random motion of charge carriers, such as electrons, in a conductor. This phenomenon occurs due to thermal agitation, meaning that as the temperature of the conductor increases, the noise level also rises. It is present in all resistive materials and is a fundamental aspect of electronic circuits. The noise is characterized by a flat spectral density, which means it affects all frequencies equally. Johnson Noise can be measured and is often quantified in terms of voltage noise density, typically expressed in microvolts per square root of hertz (µV/√Hz). Understanding this noise is crucial for designing sensitive electronic devices.