[SOLVED] Convergence problem in transient bias point calculation

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Iulian Cepoiu

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hi
I am new here and was wondering if you can help me with this error (PSPICE)

Code: 
**** INCLUDING pac-SCHEMATIC1.net ****
* source PAC
C_C1         GND N00143  1u  
R_R1         N00246 N00290  10k  
X_10k    N00290 GND N00143 SCHEMATIC1_10k 
X_U1         N00143 N00246 +15 -15 N00290 uA741

.subckt SCHEMATIC1_10k 1 2 t  
RT_10k         1 t {(1K*(1-0.5))+.001}
RB_10k         t 2 {(1K*0.5)+.001}
.ends SCHEMATIC1_10k

**** RESUMING pac-SCHEMATIC1-pac.sim.cir ****
.END

**** 10/26/14 16:55:42 ************** PSpice Lite (Mar 2000) *****************

 ** Profile: "SCHEMATIC1-pac"  [ C:\pac-SCHEMATIC1-pac.sim ] 


 ****     Diode MODEL PARAMETERS


******************************************************************************




               X_U1.dx         
          IS  800.000000E-18 
          RS    1            


**** 10/26/14 16:55:42 ************** PSpice Lite (Mar 2000) *****************

 ** Profile: "SCHEMATIC1-pac"  [ C:\pac-SCHEMATIC1-pac.sim ] 


 ****     BJT MODEL PARAMETERS


******************************************************************************




               X_U1.qx         
               NPN             
          IS  800.000000E-18 
          BF   93.75         
          NF    1            
          BR    1            
          NR    1            
          CN    2.42         
           D     .87

ERROR -- Convergence problem in transient bias point calculation


Last node voltages tried were:


These devices failed to converge:
X_U1.dc X_U1.de X_U1.dlp X_U1.fb X_U1.q1 X_U1.q2

ERROR -- Discontinuing simulation due to convergence problem
Click to expand...

 

It's a trivial problem caused by a typical PSpice beginners problem.

You'll notice that the initial transient solution shows, among other a node voltage ( GND) 3.210E+06.

"GND" isn't the PSpice reference potential. It's a node name associated with the ground symbol used in your simulation circuit. Instead you'll use the "analog ground" symbol which is connected to node "0", the actual PSpice ground node.
 
PSPICE like simulation programs don't like "floating points" and they frequenctly stop due to this error.There is a floating point in your circuit ( V_ of the OPAMP because of very high impedance ) and you'd better to connect a 1G Ohm or 100M Ohm ( for instance ) from this node to GND.
You circuit might be unstable too, check the stability by AC simulation creating Bode Gain and Phase response.
 

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