Noise floor is the measure of the noise density, in dBm/Hz, or the noise power in a 1 Hz bandwidth.

Noise can be classified into several types, including the following:

  • Shot noise
  • Thermal noise
  • Flicker noise
  • Burst noise
  • Quantization noise
  • Avalanche noise

The noise due to a matched resistive load (Ni) can be expressed as the following relation:

(Ni) = kTB watts

where

  • k is Boltzmann's Constant (k = 1.38 x 10-23J/K
  • T is the resistor temperature in Kelvin
  • B is the bandwidth in Hz

If B is set to 1 Hz, then Ni is equal to the output noise density in watts/Hz. For the system shown in the following figure, the output noise floor (NO) is the combination of the input noise multiplied by the gain or loss of the system plus the internal noise of the system (Nn).



The internal noise of a system is therefore represented by the following equation:

N n = NiG – NO