Transfer function with noise?

name

Hi,

Is it possible to calculate the gain of a closed loop system with Noise? Here's a diagram describing what i mean:

http://img206.imageshack.us/img206/8955/cltfmh8.png

I've got the following so far:

[tex]Vout = \frac{A1A2Vin}{1 + A1A2B} + [/tex] [tex]\frac{AVn}{1 + A1A2B} [/tex]

But the question is asking for the closed loop gain. Would that just be:

[tex]Vout / Vin = \frac{A1A2}{1 + A1A2B} +[/tex] [tex]\frac{AVn}{Vin(1 + A1A2B)} [/tex]


Thanks.

rbj

if the question is well posed, it needs to still specify the gain (closed loop or not) from some specified input to a specified output. your first equation (i prettied it up a little) actually shows two different transfer functions.

name

What if i do this:

[tex]A' = A2 (A1 + Vn) [/tex]

and then...

[tex]Vout / Vin = \frac{A'}{1 + A'B}[/tex]

Is this logically correct?