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AD5933 Production
The AD5933 is a high precision impedance converter system solution that combines an on-board frequency generator with a 12-bit, 1 MSPS, analog-to-digital...
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AD5933 on Analog.com

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4 wire Impedance measurement



		

			

									
					    Vikram123
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 12, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    		            		        
    Category: Hardware
    
    		        		        		    		    	
			
    Hi,
    Can I use the circuit as shown in below pictures.( it is simulated in LTspice). Can you please review the circuit. I mean is it okay to use this circuit?
    

    Our requirement is, we needed 1mA(rms) of constant current need to inject to load. In simulation it is working fine for different load values and with different frequencies.
    

     
    

    Output voltage from AD5933 IC(1.98V(p-p) with 1.48 DC bias.
    

     
    

    

    Output from Differential Amplifier

    

     
    

    

    Constant current to Body generated by Improved Howald current source circuit(PS. I am measuring current across top of current_sense resistor).
    

     
    

    

    Can we cascade this circuit with impdance measuring circuit as mentioned in below link.
    

    https://www.instructables.com/Bio-Impedance-Analysis-BIA-With-the-AD5933/
    

    

     
    

    

    

    Thanks,
    

    Vikram
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Jun 13, 2022 12:42 PM
            
            
					
      
	
      

		
		
      
					
      Hi Vikram,
      

      I see no issue with the driving circuit.
      

      It's also fine to have another amplifier driving the internal TIA as long as its DC bias point is half the AD5933 VDD. Vin is at VDD/2 and RFB pin can swing from 0V to VDD if the PGA gain is 1. You can adjust Rin and RFB to maximize the use of the dynamic range of the ADC.
      

      Best regards,
      

      Antonio
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Jun 13, 2022 12:42 PM
            
            
					
      
	
      

		
		
      
					
      Hi Vikram,
      

      I see no issue with the driving circuit.
      

      It's also fine to have another amplifier driving the internal TIA as long as its DC bias point is half the AD5933 VDD. Vin is at VDD/2 and RFB pin can swing from 0V to VDD if the PGA gain is 1. You can adjust Rin and RFB to maximize the use of the dynamic range of the ADC.
      

      Best regards,
      

      Antonio
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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