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Another "Unknown subcircuit called in" message

		
	
				

			

									
					    rdpoor
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on May 21, 2026 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user encountered an 'Unknown subcircuit' error in LTspice when using the OPAMP model without a .subcircuit directive. The solution was to correct the parentheses in the netlist and use the UniversalOpAmp1, 2, or 3 models. The wiper parameter was also adjusted to avoid a 0 ohm resistor, which can cause simulation issues.
                        	    

                
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Category: Software

    		        		            		    
Product Number:  LTSpice 

    		        		        		        
Software Version: 17.2.4

    		    		    

		    		    
		    			

			    
Issue: When I run the simulator on my circuit, I get:

Unknown subcircuit called in:
xu1 n001 input n001 opamp aol=100k gbw=10meg


What's odd is that I've not specified any .subcircuit directives.  Here's the entire net list:



*
XU1 N001 INPUT N001 opamp Aol=100K GBW=10Meg
XU2 N002 0 OUTPUT opamp Aol=100K GBW=10Meg
R1 N002 N001 10K
R2 OUTPUT N002 10K
R3 N001 INPUT {RPot*wiper}
R4 INPUT OUTPUT {RPot*(1-wiper)}
V1 INPUT 0 1
.param RPot 10k
.param wiper 0.5
.step param wiper 0.1 0.9 0.1
.tran 4m
.backanno
.end


I"m pretty sure this is a simple error on my part.  Schematic and .asc file included. 4137.Draft3.asc

			

			
									
		                             
                        

    

                                            
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                on Jun 6, 2026 8:36 PM
            
            
												
						in reply to rdpoor
					
										
			            		
    
		
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    Hi rdpoor,
    

    You asked "(Side question: what's wrong with a 0 ohm resistor?  It would be handy if that were allowed...)"
    

    SPICE doesn't allow them, that's all.  Simulations involve several trials while converging on a result.  If it ever tried it with even a femtovolt across the resistor, the current would blow up.  So it is a restriction that they put into SPICE, some 50 years ago.
    

    .step param wiper 0.001 0.999 0.1
    

    Regards,
    

    Andy
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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