andre75 wrote on Aug 26th, 2009, 3:31pm:Superposition: For each noise contributor, assume an equivalent noise source (eg. vn^2=4kTR for resistors) and calculate the transfer function while setting all other noise sources to zero (voltage zero, current open). Depends what you want to include (e.g. thermal noise of resistors and transistors) you can find a transfer function for each of the sources. The total noise at the output is simply the superposition (addition) of all individual noise sources.
In general I would use Spice, find the largest contributors and optimize those.
hi andre,
thanks for the reply. however, it is actually the very question that i asked: how to find the transfer function from a certain noise contributor to the output? spice simulation doesn't tell me the transfer function, which i need for modelling before the real design.
i mean i can derive a transfer function, but i am not sure if it is correct. it would be great if you can show me an example.