Measuring impedance with ltspice

[Telstar]

I've searched a bit and came out with this method.
I'd like to know if it is correct.

This is for the input impedance:
1. Do an AC analysis with 1V,decade
2. Plot the current in the AC source
3. Reverse it (1/I(V1) for example)
4. Change the Y axis to linear

I read amperes, but it should be ohms.
Likewise for the output resistance.

Correct or not?

 

[sawreyrw]

A better way to do this is to inject a 1 unit AC current into the node of interest. This won't upset the bias point and the node voltage is equal to the impedance of that node. No need to plot 1/I as in your method.