simulating CG LNA from razavi book. Help!

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coxstreet

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stimulating CG LNA as the step from the book. But the gain is extremely low and NF is also not well. Pls help me! using TSMC018, 5.5 GHz, narrowband lna. Thankyou！
 

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Is it me or some values are different than those presented in the book?Even the transistor ratios are different..
 

First.. How do you know Razavi has used TSMC 0.18 process ??
Second... Razavi has never terminated the output of the LNA by 50 Ohm, look at it carefully you'll see that is open circuit.That's why Gp is very low.
Third..Have ever you checked the Operating Points of MOSs??
 
Yeah those are different. I just use the steps to calculate the parameters. BUT the performance is quite bad...

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Thank you for your reply! The operating points of MOSs are OK.
Razavi is not but I want to use the process to calculate the parameters following the steps by the book. Yeah, you re right that the output of the LNA is not 50 Ohms but I am little confused about "open circuit". How can I fix the problem? Sorry for the rookie question. Thank you!
 

Don't do s-parameter simulation while the output is open circuited, do AC simulation instead..
For noise, do a simply NF simulation.
 
Yeah thank you! just finish it!
NO need to do output matching. And use the ac analysis to simulate voltage gain.
Thank you!
BigBoss said:
Don't do s-parameter simulation while the output is open circuited, do AC simulation instead..
For noise, do a simply NF simulation.
Click to expand...
 

BigBoss, I am confused about the pad capacitor in the picture of 1st floor. Is it parallel or series with Rs? Thank you!
 

coxstreet said:
BigBoss, I am confused about the pad capacitor in the picture of 1st floor. Is it parallel or series with Rs? Thank you!
Click to expand...
This capacitor represents "parasitic capacitance" of Bondpad because of metalic layer and difussion layer and it's always defined as Bondpad to GND.So, it's parallel..
 
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