Problem in measuring output Impedance of LNA !! Please advice.

[Circuits]

Hello all,

I am trying to measure the ouput impedance of LNA ( without matching circuit at the output port) . I have attached 2 set ups for calculating the Zout using S parameters.

1) First circuit includes the inductance at the drain as a load with port.

2) Second circuit includes just a port at the load.

Which set up is correct?

How do we set the port resistance for output impedance calculation ? Is there anything else that I need to set up in the port ?

Should I only ground the ac and leave the dc bias in the circuit while I am calculating the output impedance ?



Thank you in advance

 

[Circuits]

Can anyone help me with this please ? I have been working on measuring the output impedance of LNA using sp and psp.. I am very confused. Please advice.

 

[BigBoss]

Neither one..
When you do s-parameter simulation, you should terminate each port with PORT element to able to measure input and output impedances and the Gain.

 

[Circuits]

When you say port element, Do you mean by its resistance ?
If yes then how do we see whether our circuit ( Amplifier's output) output impedance is matched to 50 ohms or not ?

Thank you