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Use OP AMP(AD797) as DAC(AD5445) output buffer



		

			

									
					    williamchen
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 12, 2011 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Dear all,
    
 
    Please help me: 
    
 
    I want to use an OP AMP(AD797) as the buffer of DAC(AD5445).
    
 
    We need Positive output voltage (0~3.3V) , but the reference design use one more OP AMP and LDO (ADR03).
    
 
    I just want use just one OP AMP as I-to-V converter.
    
 
    I found this configuration:
    
 
    
 
    My question:
    
 
    (1) RL is need?
    
 
    (2) Pin RFB connect to ?
    
 
    Is the following scheme OK?
    
 
     
    
 
    Thank you in advance!
    
 
    Best Wishes,
    
 
    William
    
									
			        
		
    

				
						
        

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 15, 2011 9:24 PM
            
            
					
      
	
      

		
		
      
					
      William,
      
 
      I don't beleave either configuration is going to work for you, but have not benched either to see. I think at best you're going to see only 1/2 the range.
      
 
      As per the datasheet, the standard way to get to the possitive ourput is as shown. I don't see a way around the need to generating a negative reference into the DAC, since the amp is going to invert the signal.
      
 
      https://ez.analog.com/cfs-file/__key/communityserver-discussions-components-files/427/320e8aecea7c39045f981ddffdb9a6be.html
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Aug 2, 2018 12:25 PM
            
            
					
      
	
      

		
		
      
					
      This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

      Thank you,
      EZ Admin
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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