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BJT Area Factor discrepancy

Hi,
 
I have created two BJT models using the database.  I am getting an unusual result when I am entering the area factors for the BJT model instances. 
The two sub circuits do not give the same simulation results.  Which is the proper way for entering the area factor?  Note I have removed the .model details from the subcircuits for clarity.  The model I am using is posted below.
 
 
.SUBCKT PNP_8X 1 2 3
Q1 1 2 3  PNP1  8
.MODEL PNP1 PNP (.......) 
.ENDS
 
.SUBCKT PNP_8X 1 2 3
Q1 1 2 3  PNP1  AREA = 8
.MODEL PNP1 PNP (.......) 
.ENDS
  
.MODEL PNP1 PNP
+IS=2.6912E-18 BF=65.0 NF=1.000 VAF=52.0 
+IKF= 1.350E-3 ISE=1.256E-15 NE=2.5 BR=4.0
+NR=1.0 VAR=3.0 IKR=1.35E-2 ISC=2.691E-17
+NC=1.00 RB=177.78 IRB=4.440E-4 RBM=13.33 
+RE=33.75 RC=22.5 XTB=0.0 XTI=4.0 
+EG=1.126 CJE=3.0E-14 VJE=0.928 MJE=0.333
+TF=1.990E-11 XTF=100.0 VTF=1.50 ITF=1.350E-3 
+CJC=3.000E-14 VJC=0.732 MJC=0.45 XCJC=1.0
+FC=0.5 CJS=5.000E-15 VJS=0.655 MJS=0.0
+TR=1.990E-9 PTF=30.0 KF=1.0E-9 AF=2.0
+TNOM=25 
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I have now come to the conclusion that the area factor parameter causes the PNP models to stop working entirely.  I am not able to get any sensible results when using the previously posted pnp subckts.  When using the NPN subckts I do get a working circuit but the area factor parameter is not consistent with the .model transistor behavior.  I am working on the assumption that an AREA = 1 is equivalent to the .model by it's self.  

 

For instance, the methods below do not produce the same simulation results when entering these in the model section for a device in the database manager.

 

*Using only the model 

.MODEL NPN1 NPN (.......)  

 

THE BELOW SUBCKTs DO NOT GIVE THE SAME SIMULATION RESULTS AS THE .model METHOD

I assume the below methods are consistent but have not investigated this. 

 

*Using a subckt 

 

.SUBCKT NPN 1 2 3
Q1 1 2 3  NPN  1
.MODEL NPN1 NPN (.......) 
.ENDS 
  
*Using the AREA parameter tag
 .SUBCKT NPN 1 2 3
Q1 1 2 3  NPN  AREA = 1
.MODEL NPN1 NPN (.......) 
.ENDS 
 
*Using the AREA parameter tag
 .SUBCKT NPN 1 2 3
Q1 1 2 3  NPN  
+AREA = 1
.MODEL NPN1 NPN (.......) 
.ENDS 
  
 
  
  
 
 
 

 

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Hi Charkear,

 

What version of Multisim are you using?


Natasha Baker
R&D Engineer
National Instruments

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