After looking at the formula of shot noise and its derivation, I thought current in shot noise refer to instantaneous average current, not dc current. By instantaneous average current, I mean current that would have been obtained if not for noises. DC current, as far as my usual understanding goes, refers to dirac delta spike magnitude in zero frequency when current is fourier-transformed, or average of current over time.
Derivations heavily suggest that current being used is instantaneous average current, but all sources I looked at say current in the formula is dc current.
Can anyone clarify what is going on here? For specific context, I am thinking of noise inside MOS transistors.
So spectral shot noise density is said to be S(w) = 2q|I_d| where |I_d| is "dc" current and q is electron charge constant. Current I can be I_0 + I_1 cos(w_1 t) + I_2 cos(w_2 t) +.. with I_i being constants. and usually I_0 is said to be dc current. My question is whether I_0 is |I_d| in spectral shot noise density, or I itself is |I_d|.