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AD8337 Production
The AD8337 is a low noise, single-ended, linear-in-dB, general-purpose variable gain amplifier (VGA) usable at frequencies from dc to 100 MHz; the −3...
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AD8337 on Analog.com

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Simulation not working for certain values on the Vgain pin

		
	
				

			

									
					    sojhalb
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Feb 14, 2025 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user encountered issues simulating the AD8337's frequency response/bode plot, where the circuit acted as a strong attenuator for Vgain ≥ 0V. The final answer confirmed a problem with the SPICE model when using a single 5V supply and a reference equal to half the supply voltage. The workaround is to use dual supplies with GND as the reference. An accompanying answer noted that the single 5V supply solution has not been resolved.
                        	    

                
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Category: Software

    		        		            		    
Product Number:  AD8337  

    		        		        		        
Software Version: LTSpice v24.1.0

    		    		    

		    		    
		    			

			    
I'm considering using the AD8337 in the design and would like to simulate the frequency response/bode plot.  However when I set the Vgain to 0V or greater the simulations results show it acting as a big attenuator.  For example when Vgain = -0.2V the circuit has around 8 dB of gain as expected.  But when I test for Vgain = 0V or higher which is suppose to give higher gain than the circuit simulations fails and it has more than 200 dB of attenuation.


    


Thanks,



Sojhal

			

			
									
		                             
                        

    

                                            
                 Analog Control Variable Gain Amplifiers (VGAs)
                
                                                    
                 software
                
                                                    
                 AD8337 Spice Model
                
                                                    
                 LTSpice v24.1.0
                
                                                    
                 ad8337
                
                                        
                                            
                
                
                                
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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Feb 16, 2025 10:07 PM
            
            
						
			            		
    
		
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    Hello ,

    In addition to your circuit above, I've connected a 2.5V source to the VCOM pin as instructed on the data sheet to make sure that we are not missing something important when operating the part in single supply. But it looks like the SPICE model of AD8337 has a problem when being operated at a single supply and with a reference equal to half the +Vs. 
       

    I'll submit a request to get the SPICE model fixed. For the meantime, you can try operating the SPICE model in dual supplies. Currently, the model seems to work with dual supplies and GND as a reference as shown below: 

     
     
     

    Regards,
    Paul
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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                on Apr 24, 2026 9:07 AM
            
            
												
						in reply to ADIApproved
					
										
			            		
    
		
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    Hello, I am interested in the single 5V supply solution but haven't managed to get it working. I assume the LTSpice model has not been fixed yet, is that the case?
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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