LNA design where to start- 'step by step design procedure'

i am totally new to LNA design please any body help me 'step by step design procedure'
from selection transistors chip or packaged transistor
in put / output maching circuit how can it be prformed
how to get best gain with low NF
HOW TO Stabilize it
biasing simulation
is there any documents where it is explained step by step
please help me


thank you in advance
sarkar

lna stability

Hi,

You start with selected you transistor: Ft, S21, Nf etc
Then you start with bisasing
Stability (K>1 etc)(generally you put resistor at colector (out) to stabilize the device, also you put L and C parallel to R in order to nulling the resistor influense on S21 ),
Matching - noise circles...
that it
in general

I know that I not specifed to much but i will add some papers, in general you can find tones of papers in google!!!

David

lna designing

Hello,

I too am designing an Amplifier.
5Watts, UHF 440-470MHz. Using BJTs.

I was hoping this would be as simple as a Common Emmitter BJT in class A mode, at worst a class AB push pull design.

Unfortunately all I can find is BJTs offering perhaps at most 1W power output.

Can anyone recommend a transistor offering greatter power output or do you think I will have to rethink the design?

Cheers

lna design procedure

hi,
thank you for your kind sugggestion
actually i don't have idea about LNA design i mean from where i shuld start will it be started from input matching output matching then stability then gain circle noise cirle then biasing (and for that where i get model) .... i have lot of doubt.

again thank you more suggestion appriciated

sarkar

Re: LNA DESIGNING

darcyrandall2004 said:

Hello,

I too am designing an Amplifier.
5Watts, UHF 440-470MHz. Using BJTs.

I was hoping this would be as simple as a Common Emmitter BJT in class A mode, at worst a class AB push pull design.

Unfortunately all I can find is BJTs offering perhaps at most 1W power output.

Can anyone recommend a transistor offering greatter power output or do you think I will have to rethink the design?

Cheers

Click to expand...

If you designing amp from sracth (I mean tran) you don' have a problem try Mitsubishi , WJ, Motorola

Also with the same 1w trnasisotr you can build Balanced amp and increase P1dB.
two amps P1dB total=P1dB single + 3dB; so two of them (1w transistor) will give already 33dBm = 4w

David

Added after 3 minutes:

mahadevsarkar said:

hi,
thank you for your kind sugggestion
actually i don't have idea about LNA design i mean from where i shuld start will it be started from input matching output matching then stability then gain circle noise cirle then biasing (and for that where i get model) .... i have lot of doubt.

again thank you more suggestion appriciated

sarkar

Click to expand...

Like I said you start with searching the tran
in all big company the give models/sparameters
I am using ADS , but other will do the job also (of course freq that u design important)
after you find tran: biasing, stability, matching input (from noise and gain circles), output matching (generally conjugate).
in papers that i send you will find all steps

David

Re: LNA DESIGNING

Hello,

Low Noise Amplifier (LNA)...
First get the operating frequency, Gain, Noise Figure & specifications of the design & then choose the FET/BJTdevice from Infineon, NEC or Fijitsu, AVAGO...
Then build stable, matching, & bising networks & then analyze using simulation tools such as AWR MWO & then build the layout...
Optimize the design if it is not meeting the specifications...

See
**broken link removed**

---manju---

Re: LNA DESIGNING

hi,

i am working in DCS Band (1710MHz-1880MHz). i want to know what is the right way of an LNA design. i could start with inupt output matching here how can i start i mean first input then out put Or both at a time ( Γl and Γs are interlinked with S11,S22,S21 etc) so i don't have clear idea. like that to get max gain with low NF.
how i can tackle the issue .for biasing i have more doubt, s-parameters are already in biased condition does it mean inside the transistor chip biasing ckt already exist!
or different. then suppose biasing is given 4 V, 20 mA in s-parameter data for a chip, means, if i simply connect (with proper filtering) 4 V supply it will automatically take 20 mA current ( because biasing ckt is already exists inside the chip !) or i have to make 20 mA by adjusting resistor externally.
and one more can you please give me an idea how to select NF circle Gain circle (which gain circle i should consider there are different kind of gain circle) in ADS.

i think you will realise my doubts
hoping a kind solution
thanks in advance to you

Added after 9 minutes:

hi david,
your papers are really nice, it clears my doubts. thank you (although i know it's toomuch less !)
david, i have been in lna design in DCS band (1717mhz-1880mhz)
here should i go with lumped element for input / output matching or i follow distributed matching?

please suggest me
thank you in advance.
sarkar.

Re: LNA DESIGNING

Hi

S-parameter files are measured at different bias conditions. As you mention, you have one file where the bias is 4V, 20mA. This means the supplier have biased it and then measured tje S-parameters. YOU have to make the bias yourself if it is a discrete transistor.

Selecting NF circles depends one your NF requirement for the LNA and of cause the gain. You will see that they tend to go in opposite direction. When you select a point on a NF-circle you have selected your "Gamma_s".

I can recommend that you take a look in the excellent book by Gonzalez: "Microwave Transistor Amplifiers".

There is a good section about LNAs and gain and noise circles.

Hope it helps.

Re: LNA DESIGNING

hi
thank you for your kind help.

Re: LNA DESIGNING

mahadevsarkar said:

hi,


i have been in lna design in DCS band (1717mhz-1880mhz)
here should i go with lumped element for input / output matching or i follow distributed matching?

please suggest me
thank you in advance.
sarkar.

Click to expand...

For this freq i beleive lumped will be better. because distributed will be big!!

David