[Help-gnucap] convergence problems

[Albert Zihlmann]

Hallo,

I just tried to simulat a simple RC-shif oscillator with gnucap:

* models
* npn-bjt model from philips
.MODEL QBC547B NPN(
+    IS=2.39E-14
+    NF=1.008
+    ISE=3.545E-15
+    NE=1.541
+    BF=294.3
+    IKF=0.1357
+    VAF=63.2
+    NR=1.004
+    ISC=6.272E-14
+    NC=1.243
+    BR=7.946
+    IKR=0.1144
+    VAR=25.9
+    RB=1
+    IRB=1E-06
+    RBM=1
+    RE=0.4683
+    RC=0.85
+    XTB=0
+    EG=1.11
+    XTI=3
+    CJE=1.358E-11
+    VJE=0.65
+    MJE=0.3279
+    TF=4.391E-10
+    XTF=120
+    VTF=2.643
+    ITF=0.7495
+    PTF=0
+    CJC=3.728E-12
+    VJC=0.3997
+    MJC=0.2955
+    XCJC=0.6193
+    TR=1E-32
+    CJS=0
+    VJS=0.75
+    MJS=0.333
+    FC=0.9579 )

* simple npn bjt model
.MODEL NPN NPN(Is=1.0e-16)

* circuit description

R_R1 2 1 3.3k
R_R2 3 2 470k
V_V1 1 0 dc 9.0
Q_Q1 2 3 0 QBC547B
C_C1 5 2 47n IC=1
R_R3 0 5 4.7k
C_C2 5 4 47n
R_R4 0 4 4.7k
C_C3 4 3 47n

* what to do
.print tran  v(2)
.tran 0 0.1 1e-5 UIC
.print op v(nodes)
.op
.end


If I try with the simple NPN model all works fine, the circuit 
oscillates. If I take the BC547B model (from philips/nxp home page) I 
get following output from gnucap:


Gnucap 0.35
The Gnu Circuit Analysis Package
Never trust any version less than 1.0
Copyright 1982-2006, Albert Davis
Gnucap comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome
to redistribute it under certain conditions
according to the GNU General Public License.
See the file "COPYING" for details.
* GNUCAP - NETLIST
#Time       v(2)      
0.         0.        
very backward time step
convergence failure, reducing (itl4)
newtime=7.629395e-13  rejectedtime=1.525879e-12  oldtime=0.000000e+00  
using=1.000000e-12
tried everything, still doesn't work, giving up


Any idea whats going wrong?