Parameters of amplifier noise performance can be reflected by these two most important factors, one is voltage noise and the other is current noise.
Voltage noise is the voltage fluctuation on the condition that the input of amplifier is short circuit and without any surrounding noise. While for current noise, current noise is input current fluctuation when the input of the amplifier is open circuit and without any surrounding noise.
The typical indicator for noise amplifier is the noise density. As it is known to all, the unit of voltage noise density is nV/, and the unit of current noise density is pA/. Voltage noise includes broadband noise and low frequency noise. Broadband noise belongs to the noise which is with a flat noise density curve. In addition, amplifier also has low-frequency noise zone, and which is with a not flat noise density curve. Besides, we also name it as 1 / f noise, flicker noise, and low frequency noise.