some basic questions on LNA

[sreechoudhary]

hai all

I am very having some basic doubts please give me reply.

1.I am doing LNA design ,for single ended LNA ..when i am doing the simulations for single ended LNA and i am trying to get relation between overdrive voltage and IIP3 (keeping length constant and varying width).for single ended with out cascode stage it IIP3 will be decresing after some point.please explain me the reason .
2.for single ended with cascode (what will be happen) for the same corcuit.
3.basic question:-RLC circuit even provide amplification ..why we need transistor after tank ciruit.

 

[khouly]

when u increase the width of the transistor the gain increase coz ur increasing the Gm
so as gain increase the nonlinaer effects as IIP3 and gain compression point decrease

but the RLC doesnot give amplification coz it is a passive network , so u must need a transistor

wish this help

khouly

 

[tieuquaybk]

U can use L transformer to obtain amflification . ( eailier i'd discused with my teacher about it , at that time i had to write program on Matlab to calculate circuit 's parameters . I did some mistakes , and didn't get any amplification . I thought as khouly that passive netword does not give amplification . After doing more accurately program i got it in the end .
the reason why we'd use transistor instead of RLC may be that RLC elements have bigger size . it bandpass 's narrow , further more they bring more loss (cos L-transfomer don't work with DC current while transistor convert part of suppliment into useful signal)

 

[No one]

Hello;
What software do you use for simulation?