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Design >> Mixed-Signal Design >> A question of the input referred noise
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Message started by alixluohao on Aug 31^st, 2009, 4:59am

Title: A question of the input referred noise
Post by alixluohao on Aug 31^st, 2009, 4:59am

Hi
when reading the paper "Device Noise Simulation of Delta-Sigma Modulators", Manolis Terrovitis and Ken Kundert, www.desigers-guide.org/Analysis, I feel confused about the conclusion "The input referred noise of the open loop system is equal to that of the close loop system with feedback gain equal to one(or any other noiseless feedback)", who can give me a simple explanation if you have read this paper.
Thanks!
LUO

Title: Re: A question of the input referred noise
Post by MarcoC on Sep 8^th, 2009, 2:02am

Hi alixluohao,
I didn't read the paper you cited but I can try to help you.
The input referred noise is the same in both cases - i.e. open loop and closed loop- because - let me say- the global "transfer function" is different.
The closed loop is able to reduce the output noise but it changes also the gain in the same matter, so the input referred noise is the same.

My considerations are taken on a generic system but they should be applied also for delta-sigma.

I hope to be helpfull.

Bye,
MarcoC