calculating input impedance

[jbxvt]

i've a very simple (and stupid may be) question. i'm designing a
simple amplifier and i need to match the input and output to 50 ohms.
my question is how can i find out the impedance looking into the
gate/gate-source of the transistor so i can design an appropriate
matching network.

i did SP analysis and plotted ZM1 but that gave me an odd result so I
was wondering if i'm doig something wrong. should Z11 and ZM1 give the
same result? I also need to find out the impedance looking into the
drain for output match and I did ZM2 and again result was odd. Also,
what if i want to check impedance looking into any node; is there a
cadence way of doing it or you've to do voltage source and then
calculate R=V/I but that would just give me resistance; what about
reactance? thanks

 

[Allen]

You can run SP and then measure use the function to measure Z11, Z22...
You will see that the unit of them is ohm, make sure you measure the
real part and the imginary part separately. After that you can use
matching tool to design the matching circuit for it.


jbxvt 写道：

i've a very simple (and stupid may be) question. i'm designing a
simple amplifier and i need to match the input and output to 50 ohms.
my question is how can i find out the impedance looking into the
gate/gate-source of the transistor so i can design an appropriate
matching network.

i did SP analysis and plotted ZM1 but that gave me an odd result so I
was wondering if i'm doig something wrong. should Z11 and ZM1 give the
same result? I also need to find out the impedance looking into the
drain for output match and I did ZM2 and again result was odd. Also,
what if i want to check impedance looking into any node; is there a
cadence way of doing it or you've to do voltage source and then
calculate R=V/I but that would just give me resistance; what about
reactance? thanks