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OP42 Not Recommended for New Designs
The OP-42 is a fast precision JFET-input operational amplifier. Similar in speed to the OP-17, the OP-42 offers a symmetric 58V/µs slew rate and is internally...
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OP42 on Analog.com

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"hello world" circuit with op42

		
	
				

			

									
					    JMGL
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 24, 2013 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hello guys,
    
 
    Sorry for this post, I am guessing it is extreamly basic but I just cannot get around it.
    
 
    I am using an op42, The connections are:
    
 
    1 (NULL) -> Not connected
    
 
    2 (-IN)     -> through 10k to (6) and through 10k to signal
    
 
    3 (+IN)    -> GROUND
    
 
    4 (V-)      -> GROUND
    
 
    5 (NULL) -> Not connected
    
 
    6 (OUT)  -> through 10k to (2) and output
    
 
    7 (V+)     -> ~5V
    
 
    8 (N.C.)  -> Not connected
    
 
    This is the simplest inverting cicuit that I could make. I was just playing with the op to learn how to use it. The signal is a square function from 0 to 1.5V.
    
 
    The output of that configuration, I was expecting to be the inverted signal, nevertheless, what I obtain is a square signal with really small pk to pk and with an offset of 1.5V.
    
 
    I have also tried with other resistors pairs (100R and 100R) and what I get is a DC voltage with the input signal on top.
    
 
    Searching the web, they recomended to use a compensating resitor (with resistance equal to the parallel equivalent of the other two resistors) between (3) and GROUND, but this did not change anything at all.
    
 
    Do you have any idea of what I am doing wrong?
    
 
    Thank you
    
 
    JMGL
    
			
    
			
									
		                             
                        

    
    
                                            
                 Operational Amplifiers (Op Amps)
                
                                                    
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                 op42
                
                                                    
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                on Sep 25, 2013 7:36 AM
            
            
						
			            		
        
		
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        Hello Harry and Kris,
        
 
        Thank you very much for your quick answers. I have tried as you suggested, but there is still something that I am doing wrong.
        
 
        My connections now are (to the best of my knowledge):
        
 
        1 (NULL) -> Not connected
        
 
        2 (-IN)     -> through 10k to (GROUND) and through 10k to (6)
        
 
        3 (+IN)    -> signal
        
 
        4 (V-)      -> 0
        
 
        5 (NULL) -> Not connected
        
 
        6 (OUT)  -> through 10k to (2) and output
        
 
        7 (V+)     -> ~10V
        
 
        8 (N.C.)  -> Not connected
        
 
        This is the configuration that you suggested as a non-inverting amplifier. When I input a square signal which oscillates from 0.1V to 0.9V I obtain another square signal which oscillates from 2.8V to 7.3V (I was expecting 0.2V to 1.8V).
        
 
        I have also tried using V- = -15V and V+=15V (properly grounded) since the datasheet said maximum difference 40V (and this is the only negative voltage that I have), and I think I have fried the opamp: the output was constantly ~-13V and it got really hot. I have other one but I wanted to ask you before trying anything else.
        
 
        Thank you for your help,
        
 
        Marcos
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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                on Sep 25, 2013 7:36 AM
            
            
						
			            		
          
		
										0
					
	
          

		
		
          
		
          
                                
                                                            
          
					
          Hello Harry and Kris,
          
 
          Thank you very much for your quick answers. I have tried as you suggested, but there is still something that I am doing wrong.
          
 
          My connections now are (to the best of my knowledge):
          
 
          1 (NULL) -> Not connected
          
 
          2 (-IN)     -> through 10k to (GROUND) and through 10k to (6)
          
 
          3 (+IN)    -> signal
          
 
          4 (V-)      -> 0
          
 
          5 (NULL) -> Not connected
          
 
          6 (OUT)  -> through 10k to (2) and output
          
 
          7 (V+)     -> ~10V
          
 
          8 (N.C.)  -> Not connected
          
 
          This is the configuration that you suggested as a non-inverting amplifier. When I input a square signal which oscillates from 0.1V to 0.9V I obtain another square signal which oscillates from 2.8V to 7.3V (I was expecting 0.2V to 1.8V).
          
 
          I have also tried using V- = -15V and V+=15V (properly grounded) since the datasheet said maximum difference 40V (and this is the only negative voltage that I have), and I think I have fried the opamp: the output was constantly ~-13V and it got really hot. I have other one but I wanted to ask you before trying anything else.
          
 
          Thank you for your help,
          
 
          Marcos
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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