[SOLVED] input referred noise and bandwidth

[Winny_Puuh]

Hi guys, I have a question (again) but it's a short one this time:
if I have a bandwidth of 50kHz, a gain of 50dB --> GBW = 50dB(=316)*50k = 15.8MHz
I want to calculate the input referred noise (thermal) V = 8kT/3*(2/gm1), then I square it, integrate it and here is my question: do i have to multiply it with 15.8Mhz or 50kHz? This makes quite a difference and I dont know which one is the right one...

 

[crutschow]

If the 50kHz bandwidth is determined by a filter in the amplifier then you would use a 50kHz bandwidth to calculate the total noise.

 

[Winny_Puuh]

Thank you =) that's good news :wink: