LNA output matching network

[brjaiswal]

How do you determine the LNA output inductor(Ld) and capacitor (CL) value? I am using LC network to match output impedance of 50 ohm. My resonant freq. is 5.25GHz.

Please give me some ideas.

 

[ropt728]

You need to simulate using DC block and DC Feed to match the impedance

 

[brjaiswal]

what do u you mean by DC block and DC feed? Can you please explain it in detail?

 

[eason.RFIC]

i think it determined by two factor .first:the voltage gain at this frequency should be the maximum. second:you need achieve match at you intereted frequency. I think you can add a very big inductor at drain(10nH),and then measure the ouput impedance, then use a software like ADS to find the output match network ,usually is a parralel inductor and series capacitor .....i am a freshman.maybe we can discuss it furture

 

[brjaiswal]

I tried 7nH inductor and 500uF capacitor and getting 238 ohm output impedance, now how should I match to 50 ohm?

 

[ropt728]

what software you using ?

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You need to find out the impedance of your LNA, then do matching with Smith Chart

 

[brjaiswal]

I am using synopsis HSIM (hspicerf - cosmoscope).

Thank for reply

 

[ropt728]

I never use that before
You can find from net for the guide whether does it support any smith chart utilities in it.If yes, then it will make your work easier a lot

 

[eason.RFIC]

there are many small softwall to calculate match network with smithchart , i use "Smith V2.00", it is very convenient , and i calculate for you , the Drain inductor is 1.79nH, and series capacitor is 420f F ,thanks

 

[BigBoss]

LNA Output Matching Circuit is designed so that conjugate matching condition is satisfied.But it should be remembered that for minimum NF, input matching circuit must be optimized and therefore output
matching should also be optimized because of interaction between these two.For this, Noise Circles should carefully be examined and the other circles for input/output matching,gain,stability too..