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ADN2880 Last Time Buy
The ADN2880 is a 3.3 V, high gain SiGe transimpedance amplifier (TIA). The TIA converts the small signal current of a photo detector into differential...
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ADN2880 on Analog.com

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ADN2880 gain at 1,5GHz

		
	
				

			

									
					    pablohr88
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 30, 2015 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Good evening:
    
 
    We're looking to use the ADN2880 for a Free Space Comunications system. The signal received is at 1,5GHz, and the PIN photodiode has a capacitance of 1,25pF. This provides a max. transimpedance resistor of 106ohm, but the ADN2880 has a resistor of 1400ohm, which will limit the BW to 90MHz. Are this calculations correct or there's any way to use the device for our frecuency?
    
 
    In case not, could you recommend us a transimpedance amplifier working at 1,5GHz with the 1,25pF of the PIN photodiode?
    
 
    Thanks in advance.
    
 
    Regards.
    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 1, 2015 1:37 PM
            
            
						
			            		
      
		
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      Dear Pablo,
      
 
      ADN2880 is a good TIA device to work with a 0.8pF, or better 0.5pF PIN photo-diode, to support an optical signal receiving upto 2.5Gbps.
      
 
      ADN2880 transimpedance gain is 4,400 V/A. With an input bias of about 0.85V, its equivalent input impedance is very small (please refer to Fig. 1 of the datasheet). In another word, the TIA+PD optical receiver bandwidth is dominated by the selected photo-diode, TIA input offset, PD to TIA bonding, and the other peripherals or parasitic.
      
 
      Assume the selected photo-diode junction capacitance is 1.25pF. To get a bandwidth of 1.5GHz, the channel impedance (PD resistance + all the other serial resistance) should be less than 85ohm, in a rough estimation.
      
 
      In general, people would approach higher bandwidth support with a smaller junction capacitance photo-diode  given the channel resistance keeps as a constant after selected TIA and TIA to PD bonding circuitry.
      
 
      Hope these are what you need.
      
 
      Best Regards,
      
 
      Dongfeng Zhao
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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