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Simulation in LTSpice is distorted for suggested design from the datasheet Fig 68



		

			

									
					    Mohi
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 29, 2021 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Followed the design from Figure 68 of the datasheet to simulate the circuit in LTSpice. The design is included.
    It should work from 735uA (5mV output) to about 70mA (4.76V output). The input is a sinusoidal wave of 1kHz, and TIA is powered from ±5VDC.
    At lower input current, the output holds as expected; however, as the input current increases, the output is severely distorted. Furthermore, the output does not swing past +4V.
    What might be causing this issue in this design, and how to correct the mistakes.
    I followed the suggestions from the datasheet but cannot get it to work.
    

    Thanks.
    

    

    

    Link to LTSpice schematic:
    

    https://drive.google.com/file/d/11_Q2BlXrEec6JrLpHJhos5Hx-T3i8suF/view?usp=sharing
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Jul 15, 2021 8:11 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      

      I tried to run your circuit based on figure 68 of the data sheet.
      I replaced the C1 to 33nF from 33pF basing from the response on figure 69 for the effect of snubber circuit.
      Also, I have used discrete current source instead.
      

      The circuit able to respond for the input range you have mentioned (735uA to 70mA) but is obviously having convergence issue as the response is too slow.
      

       
      

      We will check the model and provide update.
      

      Thanks and regards!
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
			                            
                        
                on Jul 15, 2021 8:11 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      

      I tried to run your circuit based on figure 68 of the data sheet.
      I replaced the C1 to 33nF from 33pF basing from the response on figure 69 for the effect of snubber circuit.
      Also, I have used discrete current source instead.
      

      The circuit able to respond for the input range you have mentioned (735uA to 70mA) but is obviously having convergence issue as the response is too slow.
      

       
      

      We will check the model and provide update.
      

      Thanks and regards!
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

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