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ADL5565 Recommended for New Designs
The ADL5565 is a high performance differential amplifier optimized for RF and IF applications. The amplifier offers low noise of 1.5 nV/vHz and excellent...
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ADL5565 on Analog.com

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ADL5565 Common-mode Rejection Ratio



		

			

									
					    twarner
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 2, 2019 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    The data sheet shows common-mode rejection ratio on page 14, figure 24 as 57 dB at 1GHz.
    

    Using the s-parameters given for the device shows a common mode gain of  approx -32 dB in the 6 dB gain configuration at 1GHz.  The same simulation shows approx. 6 dB of differential gain, so I believe the simulation is set-up correctly.
    

    How was the common-mode rejection ratio measured?  Can I expect CMRR around 57 dB at 1GHz?  I will be using the device in a circuit that will have a significant common-mode RF signal that I want to reject.
    

    

    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
			                            
                        
                on Oct 3, 2019 2:35 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      

      Yes, I see about the same as you for CMRR when using the published S-parameters.  I'm getting around 43 dB of delta between differential vs common mode.  The datasheet value of 60 dB typical CMRR appears to be incorrect, my apologies.   
      

      Are there other important specs for your application, such as OIP3, HD2/3, etc ?   If you can share more details of the application we may be able to suggest a more suitable part number.
      

      Thanks,
      

      Darrell
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Oct 8, 2019 9:00 PM
            
            
												
						in reply to ADIApproved
					
									
        
	
        

		
		
        
					
        In our application, we are looking to receive a small differential signal on a device that is also experiencing a very high common-mode signal at an almost identical frequency.  The app is currently centered in the low GHz  region.  This will be early in the a receive chain so noise and distortion levels are important.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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