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lna design for maximum gain

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ashraff

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hi guys

im building a lna for maximum gain at 433MHz, for my btech project.. i am usin ADS software for designing. im also usin AT-41486 BJT as my active device. it is biased at at Ic=25mA at Vce = 8V, the data sheet and avago website has s2p file but is incomplete. it does not have the noise parameters..which is now puting my project on a halt...i emailed avago like 10 times and they not very helpful..anyone has used this active device and has noise parameters for various frequencies so i cn use that data and compile a s2p file to run on ADS to simulate noise figure? help needed urgently
 

Try to make s parameter analysis with using the real model file.ADS gives accurate results.If you design LNA for maximum gain your noise figure will be worse than you expected.
 

Hi Ashraff,
why dont you make nonlinear model from datasheet & use it for simulation?
Or use non linear model provided on avago website if available.
Or choose different biasing consition S2P files
The thing is ,you dont know how they have measured S parameters , so this data may not be give accurate results, either use non linear model or measure S parameters on your own.

For 433 MHz, why are you using BJT??
There so many ready made chips available.
May be you can check on google.
 

alpuslu, how do u make the s-parameter analyses, because i tried and it doesnt work....

Added after 2 minutes:

Abhishekabs, that info is not on the data sheet, so cant make a s2p file..i realised most of the actice device at Ic=25mA do not have s parameters for noise...i really dont knw why...we have to use a bjt for our project, can not use ready made chip, we designing from first principle.
 

alpuslu said:
Try to make s parameter analysis with using the real model file.ADS gives accurate results.If you design LNA for maximum gain your noise figure will be worse than you expected.
Click to expand...


Agreed. and it will also result in narrowest of bandwidth ( may not be an issue) but max gain will also increase the probability of circuit instability. Its never a good idea to max out the gain in a single device. Spreading the gain across several devices will produce a much more stable amplifier, be it for receive or transmit.

cheers
Dave
VK2TDN
 

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