how to find input and output impedance of the device

dear frns....

how to find input and output impedance of the FET using s-parametrs of that device...plzz give the formulae to calculate the impedances using s-parameters.....


thanking u..

hello

Try the following link:
http://www.rfcafe.com/references/electrical/s-h-y-z.htm

hope this helps.

Just plot S11(input) and S22(output) on a Smith chart and there are the impedance.

S11 and S22 are scattering parameters (power waves ratios), not impedance parameters. There are formulas for conversions between S, Z (impedance) and Y (admitance)

If you have access to ADS, there are built-in functions to do the job. Try the Zin function under the Simulation-S_Param menu.

Regards

Erno