# Transfer function with noise?

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Tags: function, noise, transfer
 P: 6 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: $$Vout = \frac{A1A2Vin}{1 + A1A2B} +$$ $$\frac{AVn}{1 + A1A2B}$$ But the question is asking for the closed loop gain. Would that just be: $$Vout / Vin = \frac{A1A2}{1 + A1A2B} +$$ $$\frac{AVn}{Vin(1 + A1A2B)}$$ Thanks.
 Quote by name 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: $$V_{out} = \frac{A_1 A_2}{1 + A_1 A_2 B} V_{in} + \frac{A_2}{1 + A_1 A_2 B} V_n$$ But the question is asking for the closed loop gain.
 P: 6 What if i do this: $$A' = A2 (A1 + Vn)$$ and then... $$Vout / Vin = \frac{A'}{1 + A'B}$$ Is this logically correct?