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ADF5904 Output



		

			

									
						STorvi809
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Jun 14, 2021 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hi.


I would like to know a low noise driver that can be connected to ADF5904 output without loading the ADF5904 output stage.


The driver output will be connected to ADC.


The driver specs required are Gain >10dB, 3dB Bandwidth > 10MHz and the ADC will be having input impedance of 10K.




We were using the ADA4940-2 as the output driver for our use case, with resistors RG and RF of 1K and 10K respectively for gain of 20dB.


But the output is affected by noise.


If we reduce the resistors around 200 ohms and 2K respectively, the output of ADF5904 will get loaded as the output impedance of ADF5904 is 900Ohm differential, so 450Ohm single ended.




Please let me know which output driver can be used.


Preferable two amplifiers in a single chip.




Thanks,


Sutej.

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	










	

	

					



			








	
	
	
	



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													+1
							
			
				
									
							        
            
                                                                                                        
      
                            
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                                 Analog Employees 
                                
                            
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                on Jul 6, 2021 4:09 PM
            
            
					
    
	
    

		
		
    
					
    Unfortunately we didn’t do any characterisation on output level/gain vs lower load impedances. We basically ran it into the high impedance input of the AD8130 acting as a balun.
    

    The AFE/ADC that we recommend for the ADF5904 is the ADAR7251 which has an input impedance of 2.86kOhm SE / 5.72kOhm diff.
    

    I can’t comment on how much the gain will reduce with load impedances lower than these.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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													+1
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Jul 6, 2021 4:09 PM
            
            
					
    
	
    

		
		
    
					
    Unfortunately we didn’t do any characterisation on output level/gain vs lower load impedances. We basically ran it into the high impedance input of the AD8130 acting as a balun.
    

    The AFE/ADC that we recommend for the ADF5904 is the ADAR7251 which has an input impedance of 2.86kOhm SE / 5.72kOhm diff.
    

    I can’t comment on how much the gain will reduce with load impedances lower than these.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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