the resistance that, if introduced into the input circuit of an ideal, noiseless tube, would produce at 290 K, over the appropriate frequency band, noise of the same level as that occurring in the actual tubequantity Req, having the dimensions of resistance, used to express the equivalent noise voltage En of a one port device through the relationship: where To is a reference thermodynamic temperature, fixed by convention around 290 K, ?f is the bandwidth considered and k is Boltzmann...