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Old 27th January 2011, 01:24 PM   #1
Telstar is offline Telstar  Italy
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Join Date: Dec 2007
Location: Italy
Default Measuring impedance with ltspice

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?
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Old 27th January 2011, 02:50 PM   #2
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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.
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