How to perform output matching of CS LNA
I am designing integrated common-source LNA but do not know
how to perform output impedence matching.
Some circuit contain one L and one C as load of LNA. Is there
any design rules of this L and C.
As for block cap of LNA, is there any experience value for 1G
application? 1nF or more?
by the way, if mixer follows lna, should I need perform LNA
output matching according the input impedance of mixer.
Best wishes
fxxjssc
if the Mixer will be directly connected to the LNA in the chip , and there will no filter between them , then u don't need to the matching in the case if the distance between them is close enough
but if the LNA output will be off chip , and u need a filter , then u need matching , u need to measure the LNA output impedance , and then include the pad , and bond wire inductance , so u got the total output impedance , and then design ur matching network for the filter
Khouly
Dear khouly,
I want to simulation LNA but without output matching because it will be connected to MIXER
directly.
Does the S22 mean nothing for no matching?
what about S21 and S12?
Or for my design, what should I do?
Best wishes
fxxjssc
S21 is the gain of ur LNA , the S12 the revers gain , which is important for RF feedthough
the S22 show how well ur LNA is matched with the coming stages after it
use a 50 Ohm termination and check s22
khouly
Dear khouly
Output impedance of my LNA is not 50ohm.
Is it a problem when use a 50ohm termination?
fxxjssc
no , this will just reduce the gain and u can measure the output impedance of ur LNA
khouly