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How to determaine the output impedance?



		

			

									
						xzsawq21
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 5, 2017 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hello
    
 
    I have a VCCS based on AD8130.  After many googling and studying.. now I'm frustrated!
    
 
    for checking the output capacitance usually I put a 1Kohm resistor on the output and check the 3-dB corner frequency. so the output capacitance is C=1/(2*pi*R*f3dB)
    
 
    But I really I don't know how I should calculate the output impedance of the VCCS.
    
 
    Regards
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

					
    
			
    


    

	















    
	
    
	
    
					



			








	
	
	
	



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													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Aug 18, 2017 11:58 AM
            
            
					
        
	
        

		
		
        
					
        Thank's for your attention and recommendation
        
 
        I've studied many papers about VCCS. (almost all papers )
        
 
        it is one of the first application notes that I had studied before  
        
 
        one of the worst drawback of such circuit is the mismatch between resistors.
        
 
        if you want a good accuracy it's better to use very accurate resistors (0.005% or better)  
        
 
        it's a good paper to talk about it:
        
 
        http://ieeexplore.ieee.org/document/6221965/ 
        
 
        I think AMP03 or INA105 are good choices for such application.
        
 
        so you need a unity gain feedback (I'd like to call it a moderate version)
        
 
        if you want very accurate VCCS it's better to use a DC stabilized feedback. (I'd like to call it a  advanced version)
        
 
        and ... 
        
 
        Regards
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Aug 18, 2017 11:58 AM
            
            
					
          
	
          

		
		
          
					
          Thank's for your attention and recommendation
          
 
          I've studied many papers about VCCS. (almost all papers )
          
 
          it is one of the first application notes that I had studied before  
          
 
          one of the worst drawback of such circuit is the mismatch between resistors.
          
 
          if you want a good accuracy it's better to use very accurate resistors (0.005% or better)  
          
 
          it's a good paper to talk about it:
          
 
          http://ieeexplore.ieee.org/document/6221965/ 
          
 
          I think AMP03 or INA105 are good choices for such application.
          
 
          so you need a unity gain feedback (I'd like to call it a moderate version)
          
 
          if you want very accurate VCCS it's better to use a DC stabilized feedback. (I'd like to call it a  advanced version)
          
 
          and ... 
          
 
          Regards
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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