Re: Is it right to understand the Zopt(optimized noise impedance)of ind degenarated l
Why we use Ls ?? To bring the Zin to Zopt..
Zopt is a intrinsic parameter and is not related to external component.Those components are used to match these two impedances.
thanks a lot ,Sir.
I got some equations of Zopt from the paper
**broken link removed**
The value of real part of the Zopt is the first equation. A and B1 are demenstrated by the last 2 equations. Cgs is the gate cource capacitance of the main mosfet of lna, Cex
is the externally added capacitor paralel to the gate and source of the main mosfet.α、γ、δ 、c are the process paramter ,they are intrinsic and unchangable.
If the is no Cex, then k =1,and the Re(Zopt) will be much larger than 50 ohm.So we increase the Cex.when the Cex increase,then the k increase , and so the B1 increase.Then the
Re(Zopt) decrease,
.when it decreased to 50ohm,the noise imepadence is matched.And then we justify the Ls to match input impedance of the lna to 50 ohm.If there is no Cex,we cannot get the power
matching and noise matching simultaniously.
In this method,we use Cex to justfy the real part of the optimized noise impedance to 50 ohm?