Re: [Help-gnucap] Determining impedance between two nodes...

[mcmahill]

On Mon, 7 Oct 2002, Hugo van der Merwe wrote:

> Are "newbie" questions such as these welcome on this list? :
> 
> How can I determine the impedance seen at the input and output nodes of 
> an amplifier circuit? I've tried adding e.g. Z(23) to find the impedance 
> at node 23 (my output node). I added it to my ".print ac" line, as I am 
> interested in AC small signal impedance.
> 
> This gave values at the output which looked reasonable, though I haven't 
> verified them. I want to do the same for the input, but since I had this 
> as my input:
> 
> Vin 3 0 DC 0 AC 10m
> 
> the result is of course practically 0. I tried disconnecting Vin to see 
> what it returns then, but that doesn't work, since that changes the DC 
> operating point as well.


print/plot V/I of course.  Ie, v(3)/i(Vin).

-dan