noise voltage, equivalent input (of a two-port device) (V_n)

The voltage of an ideal voltage source (i.e., one having zero internal impedance) in series with the input terminals of the device that represents the part of the internally generated noise that can properly be represented by a voltage source.

NOTE In the definition, the equivalent input noise current, which would be needed for a complete and precise description of the device noise, is neglected. If the external source impedance is zero, the noise voltage represents the total noise.

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