Products Mentioned

LTC1050 Production
The LTC1050 is a high performance, low cost zero-drift operational amplifier. The unique achievement of the LTC1050 is that it integrates on-chip the two...
Datasheet
LTC1050 on Analog.com

  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 496 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    




















	
	
			
	
		
		
	
	
		

		
LTC1050 opamp voltage follower saturation problem



		

			

									
					    Ronie88
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 5, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    

    I am using an LTC1050 precision opamp. I have applied +-5 V dual rail supply at Vdd and Vss. The output pin 6 is connected to inverted input pin 2. And pin 3 is signal input. So everything is same as an opamp voltage follower should be. 
    

    When I power up the circuit , the output voltage swings to +ve rail and in my other samples of LTC1050, it swings to negative rail when no input is connected to pin 3 and it is left floating.
    

    However when I connect actual voltage input to  pin 3 then it works fine and precise and follows the voltage properly and neatly.
    

    My concern is why does output swings to either +ve or -ve rail with pin 3 left floating ?
    

    My main issue is to interface the output to an ADC to measure both +ve and -ve voltage output but I cannot stress the input pin of ADC to -0.3 to Vdd+0.3V. I have already damaged one ADC module with this. Please suggest if Opamp is working ok and if I need ADC input protection.
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Operational Amplifiers (Op Amps)
                
                                                    
                 amplifiers
                
                                                    
                 buffer
                
                                                    
                 opamp
                
                                                    
                 voltage follower
                
                                        
                                            
                
                
                                        
                                            
                
                
                                
                    Show More
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



Parents
	
      
	

    • 
	
      






      
	
      
		
      
							
					
      
		
      
			
											
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Mar 14, 2022 1:10 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      

      From your third paragraph, I think the opamp is working properly since you said that it functions properly when there is an input voltage.
      

      Is there a reason why you need to leave the input of the opamp floating?
      

      There's a variety of reason why the output swings to the rail when the input is floating. This could be due to noise, interference, or some type of coupling from your setup.
      

      Since you're using the opamp as an interface to an ADC, you could try supplying the opamp with the same supply for you ADC +/- some tolerance. This way when your opamp saturates, it won't violate the input pin of the ADC.
      

      Thanks,
      

      Donnie
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	
    



Reply

      


    • 
	
      






      
	
      
		
      
							
					
      
		
      
			
											
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Mar 14, 2022 1:10 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      

      From your third paragraph, I think the opamp is working properly since you said that it functions properly when there is an input voltage.
      

      Is there a reason why you need to leave the input of the opamp floating?
      

      There's a variety of reason why the output swings to the rail when the input is floating. This could be due to noise, interference, or some type of coupling from your setup.
      

      Since you're using the opamp as an interface to an ADC, you could try supplying the opamp with the same supply for you ADC +/- some tolerance. This way when your opamp saturates, it won't violate the input pin of the ADC.
      

      Thanks,
      

      Donnie
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 


    


Children
	
    No Data