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LTspice26.0.1 bug: terminated TL (y2) produces overshoot.

		
	
				

			

									
					    twopif
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Feb 6, 2026 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user encountered overshoot in a terminated lossless transmission line simulation in LTspice 26.0.1, which was not present in previous versions. The overshoot can be reduced by enabling smooth half-sine transitions in the V source, but it is not fully eliminated. A significant reduction in the maximum time step (100ns to 10ps) or adding a B-source with tripdt=14ns near the input edge can resolve the issue, though the latter is more practical. The difference in time stepping protocols between LTspice 24.1.9 and 26.0.1 is likely the root cause.
                        	    
    
                
                     AI Generated Content
                
    	    
    
             
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Software
    
    		        		        		        		        
    Software Version: 26.0.1
    
    		    		    
    
		    		    
		    			
    
			    
    Hi,
    

    The terminated lossless transmission line shows overshoot at each rising/falling signal edge (see example file).
    

    With previous software releases (< 26.0.0) the same circuit is functioning well.
    

    The lossy transmission line (LTRA with R=0) can be used as work around.
    

    Issue13_LTspice26.0.1.zip
    
			
    
			
									
		                             
                        

    
    
                                            
                 software
                
                                                    
                 26.0.1
                
                                                    
                 LTspice