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Subject: Pole-Zero analysis
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Ram
Posts: 3
Online: User is Offline
9/22/2006 4:27 PM  
Hi ,

Just wondering whether is there anyway for extracting poles/zeroes from spectre simulation.

Tried PZ analysis in Spectre -> doesn't give valid poles/zeroes.


Can any one help me out ?

Thanks in advance!

Ram
adbeckett
Posts: 248
Online: User is Offline
9/24/2006 12:54 PM  
Ram,

Well, pz analysis is the way to do it. It would have helped if you'd given some details of what was wrong?

Do you have any components which have values which are frequency dependent? For example, transmission lines, or laplace controlled sources, or Verilog-A components using the laplace functions? If so, you'll need to specify the frequency of evaluation (this defaults to 1Hz).

For most normal circuits, you don't have to do anything... so some details would help.

Regards,

Andrew.
Ram
Posts: 3
Online: User is Offline
9/25/2006 9:48 AM  
Andrew,

thanks a lot for your reply!!

I was simulating the passive filter along with opamp (veriloga model) and trying to see how the filter cut-off frequency varies with op-amp gain-bandwidth.

So I am using verilogA - components using the laplace function in my circuit - for pz analysis.

Should I specify the frequency of evaluation from 1 Hz(default value) to my desired frequency(filter cut-off frequency) ?

Thanks,

Ramesh




Ramesh
adbeckett
Posts: 248
Online: User is Offline
9/25/2006 12:40 PM  
Actually you can't really analyze the poles and zeros of a circuit using the laplace function, using the method that pz analysis uses. So I don't think moving the evaluation frequency will help.

Regards,

Andrew.
Ram
Posts: 3
Online: User is Offline
9/25/2006 1:46 PM  

One comment to add:

I didn't use the laplace function.   All I want to simulate the passive filter loading an op-amp (verilog-a model) and analyze the variation of poles resulting from passive filter!!

Ramesh
adbeckett
Posts: 248
Online: User is Offline
9/25/2006 2:12 PM  
I'm confused. Previously you said you were using the laplace function.

Perhaps you need to report this to Cadence Customer Support - so we can take a proper look at this?

Regards,

Andrew.
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