ngspice transfer function

ngspice singular matrix

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

There was no dc path between node 1 and ground .
Adding a very large resistor between both nodes solved the problem
Good Bye,
Cédric

yes this how to cheat the dc bias problems for ac analys

you can do away with the resistor there it does not try to find bias point i suppose

Alternatively to avoid this problem you can add high resistances to all the analog nodes in the netlist. This is a control option given in the .OPTIONS statement. For example if you would by default want a high resistance (say 1e12) on every node, use RSHUNT=1e12 within .OPTIONS