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AD8561 offset voltage measurement



		

			

									
						balasuren
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Jan 29, 2019 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hi Team,


The Vout is getting saturated on trying to determine the input offset voltage of AD8561 through below servo circuit.


Please help to confirm whether this approach is good to proceed and also please provide your suggestion.


 


Thank you,


Bala Suren R

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	











	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
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                on Feb 13, 2019 11:00 AM
            
            
					
    
	
    

		
		
    
					
    Hi Bala,
    

    

    Since Ad8561 is a comparator I would recommend that you use a different approach in measure the offset of the comparator.
    

    you can measure the input offset by first setting the comparator to its normal compare mode.
    

    supply to +5V to the comparator.
    

    set the Vn to 0v and apply a ramp signal to the Vp pin.
    

    Using a oscilloscope monitor both input pin as well as the output.
    

    the offset is derived as the difference between the Vn and Vp voltage after the output start to change its state.
    

    For AD8561 it is expected that a transition will happen less that 8mV after the Vp signal crosses that 0v.
    

    Regards,
    

    Joven
    

    

     
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Feb 13, 2019 11:00 AM
            
            
					
    
	
    

		
		
    
					
    Hi Bala,
    

    

    Since Ad8561 is a comparator I would recommend that you use a different approach in measure the offset of the comparator.
    

    you can measure the input offset by first setting the comparator to its normal compare mode.
    

    supply to +5V to the comparator.
    

    set the Vn to 0v and apply a ramp signal to the Vp pin.
    

    Using a oscilloscope monitor both input pin as well as the output.
    

    the offset is derived as the difference between the Vn and Vp voltage after the output start to change its state.
    

    For AD8561 it is expected that a transition will happen less that 8mV after the Vp signal crosses that 0v.
    

    Regards,
    

    Joven
    

    

     
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

    • 





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