Lecture07_Noise_Feedback_2up

Lecture07_Noise_Feedback_2up - EECS240 Spring 2008 Lecture...

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EECS240 – Spring 2008 Lecture 7: Noise and Feedback Elad Alon Dept. of EECS EECS240 Lecture 7 2 Noise and Feedback Ideal feedback: No increase of input referred noise No decrease of SNR at output Practical feedback: increased noise Noise from feedback network Noise gain from elements outside feedback loop
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EECS240 Lecture 7 3 Ideal Feedback and Noise Ideal (noiseless) feedback network: Noise doesn’t change Real feedback elements have noise though… EECS240 Lecture 7 4 Real Feedback Conceptually identical to standard two port calculations Use Rs = 0 to find v i,eq 2 Rs = to find i i,eq 2 Calculations get tedious…
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EECS240 Lecture 7 5 Practical Feedback Analysis Quick approximation method: Consider loading of feedback network on the input Add a noise source associated with this element. Example: shunt feedback Loading at input is R F Æ i i 2 = i n 2 + 4kT f /R F EECS240 Lecture 7 6 Example #2: Series-Shunt Feedback Loading is R F ||R E So, noise voltage becomes: v i 2 = v n 2 + 4kT(R F ||R E ) f
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This note was uploaded on 05/23/2008 for the course EECS 240 taught by Professor Eladalon during the Spring '08 term at University of Calgary.

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Lecture07_Noise_Feedback_2up - EECS240 Spring 2008 Lecture...

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