Re: [ng-spice] Pole-zero analysis (and others)


To ng-spice@ieee.ing.uniroma1.it
From "Arno W. Peters" <a.w.peters@ieee.org>
Date Sat, 10 Jun 2000 22:05:16 +0200
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In-Reply-To <20000610213321.A14403@cgmd80028.chello.nl >; from a.w.peters@ieee.org on Sat, Jun 10, 2000 at 09:33:21PM +0200
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On Sat, Jun 10, 2000 at 09:33:21PM +0200, Arno W. Peters wrote:
> Stack backtrace is as follows:
> 
> #0  0x808dd77 in alter ()
> #1  0x808c4ef in CKTpzRunTrial ()
> #2  0x808b196 in CKTpzFindZeros ()
> #3  0x8089ad3 in PZan (ckt=0x80ff408, reset=1) at pzan.c:59
> #4  0x807e6b5 in CKTdoJob (inCkt=0x80ff408, reset=1, inTask=0x80ff770)
>     at cktdojob.c:130
> #5  0x806e5f0 in if_run (t=0x80ff408 "", what=0x80b6889 "run", 
>args=0x8100200, 
>     tab=0x80ff390) at spiceif.c:188
> #6  0x806badb in dosim (what=0x80b6889 "run", wl=0x0) at runcoms.c:237
> #7  0x806bbc7 in ft_dorun (file=0x0) at runcoms.c:275
> #8  0x8053843 in main (argc=1, argv=0xbffff974) at ./main.c:619
> 
> I have not yet been able to determine the cause of this segfault.

Update: This crash was because I enabled PZDEBUG and the code tried to
dereference a NULL pointer and print the result.

The results of the modified circuit are:

                               Multistage filter
---------------------------------------------------------------------
Index  pole(1)                         pole(2)                         
---------------------------------------------------------------------
0      -5.500000e+07,  0.000000e+00    -1.000000e+08,  1.833176e-301   
^L
                               Multistage filter
---------------------------------------------------------------------
Index  pole(3)                         
---------------------------------------------------------------------
0      -1.000000e+08,  -1.833176e-301  


Three poles for a first order circuit?

Regards,
-- 
Arno

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