how to calculate s parameters of a transistor

Dear All,

I have just started the LNA design and decided to use NXP BFG424F NPN Transistor.

I am very new to RF Design and don?t know how to meausre or calculate or simulate the S parameters of the transistor.
Transistor Datsheet does not have S parameter for frequency I am interested.

I would appreciate if someone can help me out

Thanks in Advance

Mystery

http://www.nxp.com/models/spicespar/data/BFG424F.htm
Try to extract s-parameters using spice model provided by NXP will be the easiest way. Otherwise you have to measure s-parameters using a VNA. You will need a bias tree and a test figture.

You could make a simple SNA you will not get phase but you will get reflection and transmission power.

you use two directional couplers on your system connected to diode detectors, and do the math very simple RF, cost a little bit and takes some time... if you just want to see output power you can just connect your amp to a diode detector (maxim-ic has several good ones).

Hope this helps if you have questions let me know.

Thanks Boy/ b4bb for your help :)

You don't need to extract S-parameters from the SPICE file. S-parameters are already in this file:

http://www.nxp.com/models/spicespar/...ip/BFG424F.zip

Verify it before, the measured s-parameters may not contain package parasitics such as emitter extrinsic inductance, pin intercapacitances etc..
At higher frequencies, these can create serious troubles..

he said that s-parameters data does not contain values at frequency he is interested.