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LT6375 Recommended for New Designs
The LT6375 is a unity-gain difference amplifier which combines excellent DC precision, a very high input common mode range and a wide supply voltage range...
Datasheet
LT6375 on Analog.com

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LT6375 offset voltage issue

		
	
				

			

									
					    HardwareWave
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 21, 2020 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hi,
    

    I am using LT6375 as a unity gain amplifier for current sensing application. For current sensing 0.025 ohm series resistor is used. LTC6371 is giving output voltage of 0.110V for zero input current. It is configured as highlighted in below image.
    

     
    

    I tried another configuration to reduce the offset voltage, with below highlighted configuration i am getting 0.063V output voltage for zero input current. As per datasheet output voltage should be maximum 0.450 mV. Please do suggest ways to reduce the offset voltage. Any suggestion will be appreciated.
    

       
    

    Please do let me know in case you want more info.
    
			
    
			
									
		                             
                        

    
    
                                            
                 amplifiers
                
                                                    
                 Specialty Amplifiers
                
                                                    
                 Difference Amplifiers
                
                                                    
                 LT6375
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Oct 26, 2020 3:46 PM
            
            
						
			            		
      
		
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      Difference amplifiers will have two sources of error-- the Vos and the CMRR. The Vos is specified with a minimal common-mode component so CMRR can be neglected. In a current-sense application, there will generally be a significant common-mode applied and the CMRR will [vastly] dominate, leading to higher than expected errors as noted. This is the reason that there are specialized ICs designed to perform current-sensing, namely using topologies that are relatively immune to applied common-mode. A typical current sense circuit will have gain set high enough that the Vos will not be amplified needlessly large, but enough to provide scaling appropriate for the max current to be measured, so typical values range from 20-50. For best precision, a 'zero-drift' or 'chopper-stabilized'  input structure is desirable (for example, LTC6102).
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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