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AFE for AD7768-4



		

			

									
						juli4n
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 30, 2019 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi, I am attempting to design an analog input circuitry based on the AD7768-4. The application calls for a single-ended, AC-coupled input, with a range of +/- 8V. Max frequency is ~100kHz.
    

    I am looking for suggestions/reference design for this particular application, specifically suggestions as to what front-end amplifier is suitable. I am also open to suggestions to use ADC chips other than the AD7768-4.
    

    The end product is a portable vibration data logger, interfacing with IEPE vibration transducers. Any suggestions greatly appreciated.
    

    Thanks.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

					
    
			
    


    

	















    
	
    
	
    
					



			








	
	
	
	



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                on Mar 28, 2020 2:22 AM
            
            
					
        
	
        

		
		
        
					
         I know it's old, but it might be of help to others reading.
        

        Take a look at the AD8475.  From the datasheet:
        

        The AD8475 is a fully differential, attenuating amplifier with integrated precision gain resistors. It provides precision attenuation (by 0.4 or 0.8), common-mode level shifting, and single-ended-to-differential conversion along with input overvoltage protection. Power dissipation on a single 5 V supply is only 16 mW.  The AD8475 is a simple to use, fully integrated precision gain block, designed to process signal levels of up to ±10 V on a single supply.
        

        With a 150Mhz small signal and 15Mhz large signal bandwidths and a settling time of less than 50ns, it should be able to process any signals for input into the AD7758-X.  I would use an INAmp in front though with those signals.
        

        I used it to condition a 7Vpp 1.2Mhz complex signal for input into a 3.3V differential 5Msps 12bit ADC.
        

        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Mar 28, 2020 2:22 AM
            
            
					
          
	
          

		
		
          
					
           I know it's old, but it might be of help to others reading.
          

          Take a look at the AD8475.  From the datasheet:
          

          The AD8475 is a fully differential, attenuating amplifier with integrated precision gain resistors. It provides precision attenuation (by 0.4 or 0.8), common-mode level shifting, and single-ended-to-differential conversion along with input overvoltage protection. Power dissipation on a single 5 V supply is only 16 mW.  The AD8475 is a simple to use, fully integrated precision gain block, designed to process signal levels of up to ±10 V on a single supply.
          

          With a 150Mhz small signal and 15Mhz large signal bandwidths and a settling time of less than 50ns, it should be able to process any signals for input into the AD7758-X.  I would use an INAmp in front though with those signals.
          

          I used it to condition a 7Vpp 1.2Mhz complex signal for input into a 3.3V differential 5Msps 12bit ADC.
          

          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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