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Design >> RF Design >> Equation for noise power delivered to a matched load
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Message started by kataria0 on Dec 22^nd, 2008, 8:00am

Title: Equation for noise power delivered to a matched load
Post by kataria0 on Dec 22^nd, 2008, 8:00am

Hi
Please detect my mistake in equation for noise power delivered to a matched load, where the source impedance is purely a resistor.

Current noise power generated by resistor (In^2)=4KT/R (V^2/Hz)

Since Source resistance=load resistance => 2 resistors in parallel from noise equivalent current source in parallel with source resistance. Hence effective resistance= R/2 from current noise perspective.

Hence net o/p noise power= In^2 *(R/2)^2
=KTR
but books say KT instead. I am getting the dependance on R as well. I would appreciate if you could please point out my mistake here.
Thank you very much

Title: Re: Equation for noise power delivered to a matched load
Post by aaron_do on Dec 22^nd, 2008, 5:34pm

Hi,

not really much of a mistake. You've calculated o/p noise voltage squared. o/p noise power is,

Vn^2/R = kTR/R = kT

cheers,
Aaron

Title: Re: Equation for noise power delivered to a matched load
Post by kataria0 on Dec 23^rd, 2008, 5:29am

Thanks Aaron