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ADA4528-1 Production
The ADA4528-1/ADA4528-2 are ultralow noise, zero-drift operational amplifiers featuring rail-to-rail input and output swing. With an offset voltage of...
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ADA4528-1 on Analog.com

ADR441 Production
The ADR440/ADR441/ADR443/ADR444/ADR445 series is a family of XFET® voltage references featuring ultralow noise, high accuracy, and low temperature drift...
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ADR441 on Analog.com

AD7173-8 Recommended for New Designs
Fast settling, highly accurate, low power, 8-/16-channel, multiplexed ADC for low bandwidth input signals with integrated input buffers. Integrated precision...
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AD7173-8 on Analog.com

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ADA4528-1 as an ADC Reference Buffer

		
	
				

			

									
					    jfitzger131
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Aug 25, 2015 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Can the ADA4528-1 handle large capacitive loads ( > 4.7µF) and drive the reference of a high precision sigma-delta like the AD7173-8?
    
 
    I do not want to add source resistance between the output of the amp and the input of the reference of the ADC.  Will the 200kHz noise from the chopping frequency affect the performance of the converter without a filter?  Perhaps a snubber network is advised if the ADA4528 is to be used in this application?
    
 
    - James
    
			
    
			
									
		                             
                        

    
    
                                            
                 Operational Amplifiers (Op Amps)
                
                                                    
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Aug 31, 2015 10:22 PM
            
            
						
			            		
      
		
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      This discussion has been ongoing last week via email and closed.
      
 
      In summary, below is an excerpt of the email exchange:
      
 
      " I have sometimes seen customer use ZD amps to buffer a reference output. What they would do is LPF the output of the amp. This however increases the impedance seen at the ADC REF pin (I believe the offset voltage due to current flowing through the resistance can be calibrated out). Also, the ADA4528 cannot drive 4.7uF without any compensation. It can only safely drive up to maybe 200-300pF. So, in this case, having an post RC network serves to isolate the cap load, stabilize the amp and provide filtering.
      
 
      We haven’t tested any reference buffers with the AD717x family of ADCs for two reasons:
      
 
        
  
      1. The references we’ve used and recommended are able to drive the ADC without additional buffering required, just external RC. These are the ADR44x and ADR455x family of references.
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      2. The ADC has integrated reference buffers eliminating the need for external buffers. These buffers are not very low noise but still should be lower noise than the reference itself. The integrated buffers are chopped also so no need to worry about 1/f noise or drift. "
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                on Jan 4, 2023 6:14 PM
            
            
												
						in reply to ADIApproved
					
										
			            		
        
		
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        Can you please provide an example for a post RC network serves to isolate the cap load, stabilize the amp and provide filtering so the ADA4528 can drive 4.7uF?
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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