Re: gEDA-user: ngspice transfer function

[r <nbs.public@xxxxxxxxx>]

Hi,

There is no DC path from node '1' to the ground (node '0'). Add a
large resistor between them and the simulation will work:

Tranfer function
ISRC 1 0 AC 1
R1 1 2 1k
C1 2 3 1u
R2 3 0 1k
C2 3 0 1u
R10 1 0 1e+12
.AC DEC 10 1 10K
.END

Actually, Ngspice tried to fix it by inserting GMIN to the circuit (a
small conductance between each node and the ground) but for some
reason it didn't work. Does anyone knows why?

Cheers,
-r

On Sun, Aug 23, 2009 at 10:23 PM, cedric<cedric_libre@xxxxxxx> wrote:
> Hi,
> I am a ngspice newbie and I'd like to get a frequential transfer
> function of a Wien filter
> as an exercise .
> I'd like to plot V(3)/ISRC versus frequency .
>
> Here is the .sch file I simulate :
>
> Tranfer function
> ISRC 1 0 AC 1
> R1 1 2 1k
> C1 2 3 1u
> R2 3 0 1k
> C2 3 0 1u
> .AC DEC 10 1 10K
> .END
>
> Here is the result I get :
>
> ngspice 1 -> run
> Doing analysis at TEMP = 27.000000 and TNOM = 27.000000
>
> Warning: Source isrc has no value, DC 0 assumed
>
> Warning: singular matrix: check nodes 1 and 1
>
> Note: starting dynamic Gmin stepping
> Trying gmin = 1.0000E-03 Note: One successful Gmin step
> Trying gmin = 1.0000E-04 Note: One successful Gmin step
> Trying gmin = 1.0000E-05 Note: One successful Gmin step
> Trying gmin = 1.0000E-06 Note: One successful Gmin step
> Trying gmin = 1.0000E-07 Note: One successful Gmin step
> Trying gmin = 1.0000E-08 Note: One successful Gmin step
> Trying gmin = 1.0000E-09 Note: One successful Gmin step
> Trying gmin = 1.0000E-10 Note: One successful Gmin step
> Trying gmin = 1.0000E-11 Note: One successful Gmin step
> Trying gmin = 1.0000E-12 Note: One successful Gmin step
> Trying gmin = 1.0000E-12 Note: One successful Gmin step
> Warning: singular matrix: check nodes 1 and 1
>
> Warning: Dynamic Gmin stepping failed
> Note: starting source stepping
> Supplies reduced to 0.0000% Warning: singular matrix: check nodes 1 and
> 1
>
>
> Trying gmin = 1.0000E-02 Note: One successful Gmin step
> Trying gmin = 1.0000E-03 Note: One successful Gmin step
> Trying gmin = 1.0000E-04 Note: One successful Gmin step
> Trying gmin = 1.0000E-05 Note: One successful Gmin step
> Trying gmin = 1.0000E-06 Note: One successful Gmin step
> Trying gmin = 1.0000E-07 Note: One successful Gmin step
> Trying gmin = 1.0000E-08 Note: One successful Gmin step
> Trying gmin = 1.0000E-09 Note: One successful Gmin step
> Trying gmin = 1.0000E-10 Note: One successful Gmin step
> Trying gmin = 1.0000E-11 Note: One successful Gmin step
> Trying gmin = 1.0000E-12 Note: One successful Gmin step
> Note: One successful source step
> Supplies reduced to 0.1000% Warning: singular matrix: check nodes 1 and
> 1
>
> Supplies reduced to 0.0000% Warning: singular matrix: check nodes 1 and
> 1
>
> Warning: source stepping failed
>
> AC operating point failed -
>
> Last Node Voltages
> ------------------
>
> Node Last Voltage Previous Iter
> ---- ------------ -------------
> 1 0 0
> 2 0 0
> 3 0 0
>
> doAnalyses: iteration limit reached
>
> run simulation(s) aborted
>
> Does someone has an idea about what's wrong in the scheme file ?
> Thanks for your help,
> ced
>
>
>
>
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> geda-user@xxxxxxxxxxxxxx
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>


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