[ECE PhiBar] Noise Amplification
drobl at andrew.cmu.edu
Wed Mar 19 14:31:12 EDT 2008
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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