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ADA4000 comparator



		

			

									
					    Jajajib
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Feb 19, 2013 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi AD,
    
 
    is the ADA4000-1 can be used as a comparator instead of amplifier and is it a dedicated op-amp to work for this kind of use (e.g comparator)
    
 
    It seems that ADA4000 is highly sensitive working as a comparator and it doesn't like this non linear mode. 
    
 
    Moreover with a transistor on the output which could create high DV/DT for example.
    
 
    thanks for your help,
    
									
			        
		
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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                on Mar 13, 2013 8:10 AM
            
            
					
        
	
        

		
		
        
					
        Thx for your help David, 
        
 
        I understand the black box problem. I will think about it.
        
 
        In addition, and in order to find the root cause of failure, I have tested each op-amp by wiring them as an inverting circuit (Gain = -2). I inject a DC voltage source between 0V up to 20V on the inverting input of op-amp (not recommanded regarding the datasheet when op-amp is power supplied by +15V/-15V) and non inverting input is wired to ground.
        
 
        2 failure modes are raised. 
        
 
        - output is always equal to -Vsat (i.e close to -13,7V or -14V) whatever input voltage is between 0V and 20V.
        
 
        - output follow the inverting input, as to know the voltage source, and op-amp clamps output voltage to 15,7V or 16V when voltage source is between 15V and 20V.
        
 
        I try to find a common failure mode, any idea on what I can do on my black boxes  ?
        
 
        Additional clue : it is possible that sometimes I have injected a DC voltage source on inverting and non-inverting inputs before powering op-amp on +/-Vcc. Not recommanded too isn't it ?
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Mar 13, 2013 8:10 AM
            
            
					
          
	
          

		
		
          
					
          Thx for your help David, 
          
 
          I understand the black box problem. I will think about it.
          
 
          In addition, and in order to find the root cause of failure, I have tested each op-amp by wiring them as an inverting circuit (Gain = -2). I inject a DC voltage source between 0V up to 20V on the inverting input of op-amp (not recommanded regarding the datasheet when op-amp is power supplied by +15V/-15V) and non inverting input is wired to ground.
          
 
          2 failure modes are raised. 
          
 
          - output is always equal to -Vsat (i.e close to -13,7V or -14V) whatever input voltage is between 0V and 20V.
          
 
          - output follow the inverting input, as to know the voltage source, and op-amp clamps output voltage to 15,7V or 16V when voltage source is between 15V and 20V.
          
 
          I try to find a common failure mode, any idea on what I can do on my black boxes  ?
          
 
          Additional clue : it is possible that sometimes I have injected a DC voltage source on inverting and non-inverting inputs before powering op-amp on +/-Vcc. Not recommanded too isn't it ?
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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