[ECE PhiBar] Noise Amplification

Douglas Robl drobl at andrew.cmu.edu
Wed Mar 19 14:31:12 EDT 2008

Hey Everyone,

Once again,electrical engineering is responsible for proving something 
that we knew to be true all along.  In RF amplifier design, one of the 
more desirable characteristics is to have low noise.  As you may or may 
not know, noise can come from lossy elements.  This can be the input, or 
source, of your circuit, or things that you put into your design.  
What's interesting is that in MOS devices, some noise sources are 
correlated together.  Your source admittance, Ys can be proken up into 
Gs + jBs.  But when you work through the equations, you find that you 
can add a device to cancel the imaginary part of your admittance, thus 
making your noise lower.  Thus the stirring realization that we all 
knew: "You can lower noise if you get rid of Bs."  What's left is still 
kinda noisy, but you need that if you're going to be keeping it real.

See you at 9.  No Bs this week, or Kilo Delta.


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