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LTC6242 voltage follower output saturation voltage



		

			

									
						Peck
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Sep 21, 2018 
				
			
			
		


				
		

		    		    
		    
		    	
			
I used LTC6242 as a voltage follower configuration: - power to IC is 4.2V


- measured V+ to IC is 3.8V


- V- is feedback to Vout, measured about 3.6V


- output is set at high impedance for testing


(Note that I wanted output to be 3.8V)




When the power is at 4.2V, output seems to be saturated at 3.6V even I increased the V+ voltage higher.


Has anyone tested the saturation level of this op amp?


Other than increasing the power supply, any other method?


 

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	














	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
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                on Sep 23, 2018 6:47 AM
            
            
					
    
	
    

		
		
    
					
    Hi,
    

    Please be mindful of the input common voltage range of this opamp.  You are using a slightly lower supply voltage of 4.2V, the closest specified supply voltage in the datasheet could be referenced at Vsy=5V to ground. At Vsy=5V, the max input voltage range is 3.5V, which could mean that at Vsy=4.2V to ground, the max input range can be safe to assume to be lower. So, in the part of your circuit where you want to output 3.8V from a supply of 4.2V, your input due to voltage divider is 3.8V which is greater than the max input voltage of 3.5V or less. You must always operate the opamps in its specified supply, input, output voltage range limits. This tutorial can help you to further understand these concepts.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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													+1
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Sep 23, 2018 6:47 AM
            
            
					
    
	
    

		
		
    
					
    Hi,
    

    Please be mindful of the input common voltage range of this opamp.  You are using a slightly lower supply voltage of 4.2V, the closest specified supply voltage in the datasheet could be referenced at Vsy=5V to ground. At Vsy=5V, the max input voltage range is 3.5V, which could mean that at Vsy=4.2V to ground, the max input range can be safe to assume to be lower. So, in the part of your circuit where you want to output 3.8V from a supply of 4.2V, your input due to voltage divider is 3.8V which is greater than the max input voltage of 3.5V or less. You must always operate the opamps in its specified supply, input, output voltage range limits. This tutorial can help you to further understand these concepts.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

    • 





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