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AD8610 Production
The AD8610 (single) and AD8620 (dual) are very high precision JFET input amplifiers featuring ultralow offset voltage and drift, very low input voltage...
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AD8610 on Analog.com

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AD8610

		
	
				

			

									
					    USB
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Apr 20, 2026 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user is designing a 1 A precision current source and seeks a replacement for the AD8610, which is not marked as not recommended for new designs. The ADA4620 is suggested as an alternative. The 10 kΩ and 10 MΩ resistors in Figure 5 protect the input signal and provide a DC return path for the op-amp's input bias current, respectively.
                        	    

                
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Category: Hardware

    		        		            		    
Product Number:  AD8610 

    		        		    		    

		    		    
		    			

			    
    

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    I am designing a voltage‑controlled 1 A precision current source for calibrating a current sensor. I found Analog Devices application note AN‑968, in which Figure 5 suggests a voltage‑controlled current source topology. The recommended IC, AD8610, is not recommended for new designs by Analog Devices.
    

      

    • What other suitable ICs can replace the AD8610?
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    • If a different IC is used, will the compensation components remain the same, or do they need to be changed?
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    • Please suggest how to calculate the compensation components for the newly suggested part.
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    In Figure 5, what is the purpose of the 10 kΩ and 10 MΩ resistors connected to the non‑inverting input?
    

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Apr 30, 2026 1:47 AM
            
            
						
			            		
    
		
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    Hello USB,
    

    

    Upon checking the product status, AD8610 is still in production and is not marked as not recommended for new designs. It can still be used in new designs if it meets the requirements of the application. If you prefer to consider an alternative, the ADA4620 is a recommended option. 

    Regarding the compensation components, if you plan to change the IC in your setup, could you confirm whether the same MOSFET will still be used? 

    

    

    

    With respect to Figure 5 in AN-968, the 10 kΩ resistor protects and isolates the input signal. It also ensures impedance matching between the inverting and non-inverting inputs. While the 10 MΩ resistor prevents the non‑inverting input from floating by providing a DC return path for the op‑amp’s input bias current.
    

    

    

    Best Regards,
    Kyla
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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                on May 4, 2026 6:24 AM
            
            
						
			            		
    
		
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    Thanks for the reply.
    

    I tested this circuit for a DC application using an OPA196 op‑amp and an IRF1405 MOSFET, as I do not have the AD8610 and IRF640N. All other components remain the same.
    

    I faced the following issues:
    

    A high‑frequency oscillation was generated at the op‑amp. I understood that the original values of 22 pF and 56 Ω are not right compensation components when using the IRF1405, which has a gate capacitance of approximately 5.4 nF. To address this, I increased the capacitor value from 22 pF to 10 nF and the resistor value from 56 Ω to 470 Ω. This resolved the problem. For example, with a 2 V input, an output current of 1 A is generated.
    

    When the input is floating, the op‑amp output goes to 5 V, the non‑inverting terminal sits at 2.6 V, and the MOSFET turns fully on. As a result, the power supply connected to the MOSFET drain enters constant‑current (CC) mode.
    

    I then connected the circuit as shown below, and it worked correctly. My question is whether it is acceptable to operate the circuit in this manner. As per my understanding, the input bias current path is provided through the 10 kΩ resistor to ground. What is the role of the 10 MΩ resistor? Can it be removed?
    

     
    

    

    


    
Input 
Pull down Resistor
Series Resistor
10Mohms
Op-amp output
Op-amp non inverting (TOP)
Current output

    

    
Float
No 
10k
Yes
5V
2.6V
1.1A with CC mode

    

    
Float
10K
10k
Yes
0V
0V
0A

    

    
2V
10K
10k
Yes
4.4 V
0.201
0.996A

    
    

    

    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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