Hi everybody,

I try to simulate an RLC circuit depicted in the following figure.
http://www.4shared.com/office/06jVwNhe/GlobalmodelSpice.html
I have noticed that ngspice is not able to compile two capacitors which are connected in series. The netlist is written as follws:

*The global plasma model   
VRF 0 1 SIN(0 100 0.275732) 
CBC 2 1 5.25154 
Cs 3 2 0.1407107F 
RB 4 3 5.25154 
LB 5 4 212.692 
VG 0 5 dc 10 
.END

this circuit can't be solved transient. I get the following error or warning message :

Warning: vrf: no DC value, transient time 0 value used Warning: singular matrix: check nodes 2 and 2 Note:
Starting dynamic gmin stepping

I would be very grateful, if somebody can give me a Hint on what went wrong. best regard Nina

 

Two capacitors in series don't have a ground path at their junction and Spice can not handle that since the DC level is undefined at that point. Either combine the two capacitors into one equivalent capacitor or place a large (say 100meg ohm) resistor from the junction to ground.

Note: A 5.25154 farad capacitor is very large.

 

Hallo Zapper, thank you very much. It works now!