Consider the circuit in the attached picture.
R2 and R3 are noiseless. and V1 = (4*k*T*R1*B)
if C1 was not in the circuit, it would be possible to use the following equation and calculate the output noise voltage.
V0 = R3*V1/(R1 + R2 + R3)
However I do not know how to calculate the output noise if C1 exists.
In the following link, the noise analysis of a RC is explained. In the text a "Brick Wall" technique is described. I have no idea how to use this technique and I could not find any reference for that.
http://jcatsc.com/media/TechnicalReports/17-Noise2.pdf
If any body knows how to calculate the output noise voltage of current, please help me.
The "brick wall" is just an approximation. Rather than knowing the exact frequency response, it is assumed 100 % transmission in the pass band, and 0 transmission in the stop band. Since that is just a rectangle when graphed, it looks like a brick wall. A real filter can't actually have that response, but since it makes the math easier you can use it as an approximation.
Dear MOJTABA,
Do you still need help or did you solve the problem? I am ready to help you but you have to tell me.
The RC circuit in the figure is not complicated. I am sorry you can not connect the voltage noise source Vn of R1 across its terminal as indicated in the figure.The noise source Vn, the root mean square value, must be connected in series with R1. In this way your equation V0 = R3*V1/(R1 + R2 + R3)
will be correct. AS said by mohamed atef you need only to replace R2 by R2/(1+jwC1)
and V1=square root of (4kTR1)
After that you have to integrate th the square of Vo with frequency w from zero to infinity.
The integration will be the required answer.
I am ready to help you further.
wish you success.
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