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multi-stage lna matching

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I want to design a four stages lna. It use a common source w/ inductive deg as input and cascode a common gate as second stage, and then use another cs w/ind deg as third stage and cascode a cg again. my question is do i need to make each stage match? like first stage's output impedance match second stage's input impedance.
 

Input Stage Pair ( first CS+CG) should be matched for Minimum Noise Figure, other should ( Second CS+CG) be matched for Maximum Gain (Conjugate Matching).
Be careful about Stability Factor and a Matching Circuit is not used between CS and CG.( due to well known natural reason )
 
A bit more data would be useful, how much is the operating frequency? If the wavelength is much smaller than the distances between the stages matching is not necessary unconditionally. Stability of four stages is more relevant, this is not common I think to use 4 RF low noise amplifier in series, maybe at direct receivers.
 

Hi Bigboss
How should I match cg output? I simulated the S22 on smith chart and it is almost pure imaginary part. I tried to add some L or C to match to 50ohm and it is not work.

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My frequency is 40GHz. I want to cascade 2 cs with cascode lna to reach the gain of requirement.
 

SDRookie said:
Hi Bigboss
How should I match cg output? I simulated the S22 on smith chart and it is almost pure imaginary part. I tried to add some L or C to match to 50ohm and it is not work.
My frequency is 40GHz. I want to cascade 2 cs with cascode lna to reach the gain of requirement.
Click to expand...

Can you post your schematic,S22 on Smith Chart,S11 on Smith Chart, here ??
Why do you use CS+CG configuration ?? Is the Bandwidth large ??
CS+CG is a bit unusual for 40 GHz ( even theoretically possible ) .. Are you obliged ??
 

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