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Design >> Analog Design >> SNM or Input Referred Noise?
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Message started by sirous black on Jun 20^th, 2007, 11:47pm

Title: SNM or Input Referred Noise?
Post by sirous black on Jun 20^th, 2007, 11:47pm

Hi ,

I have a ckt and am confused over the kind of noise analysis to be done :-/ Would a Static Noise Margin analysis be sufficient to quantify the noise threshold or should input referred noise be measured?
I did run an analysis using ADE, but the value for input referred noise is unaccetpably large (in the range of mv/√Hz)!! most docs state nV/√Hz as typical value for IRN.

Title: Re: SNM or Input Referred Noise?
Post by carlgrace on Jun 27^th, 2007, 5:28am

Sirous,

I think the confusion may stem from the IRN you are looking at. In the circuit, the inputs are currents, so an IRN measured in voltage will not be appropriate. You should measure the IRN in something like pA/√Hz. That may help. Also, it looks like your circuit is maybe some kind of sense amp for a RAM? If so, IRN is probably not the most convenient way to specify noise performance. You may want to think of the noise as almost a random offset current, since that will help you to visualize it. generally, in a sense amp, you have prior knowledge of how much the input signal will swing (current in this case) so it isn't hard to specify a 3-sigma noise value.

Good luck,
Carl