Since all resistors exhibit voltage fluctuations that are proportional to their temperature, an effect known as Johnson noise, a reduction of temperature is often the only way to achieve the required sensitivity.
12.
In 1928 the thermal noise in a resistor was first measured by John B . Johnson, and Harry Nyquist provided the theoretical analysis; this is now termed " Johnson noise ".
13.
In 1951 Herbert Callen and Theodore Welton proved the quantum fluctuation-dissipation theorem ( FDT ) which was originally formulated in classical form by Nyquist ( 1928 ) as an explanation for observed Johnson noise in electric circuits.
14.
In this sense, the Johnson noise of an RC circuit can be seen to be inherent, an effect of the thermodynamic distribution of the number of electrons on the capacitor, even without the involvement of a resistor.
15.
At those lower frequencies atmospheric noise ( static ) and man-made noise ( interference ) dominate over the noise generated inside the receiver itself ( " thermal " or " Johnson noise " ).
16.
The first cathode ray tube to use a hot cathode was developed by John B . Johnson ( who gave his name to the term Johnson noise ) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922.
17.
1 Hz noise floor : calculating the noise power available in a one hertz bandwidth at a temperature of " T " = 290 K defines a figure from which all other values can be obtained ( different bandwidths, temperatures ) . 1 Hz noise floor equates to a noise power of " 174 dBm so a 1 kHz bandwidth would generate " 174 + 10 log 10 ( 1 kHz ) = " 144dBm of noise power ( the noise is thermal noise, Johnson noise ).
