While looking into integrator op-amp circuits, I came across two different implementation.

In one the non-inverting terminal is grounded . While in the other there is a resistor in between.

Can someone shed some light what is the function if the resistor? Is there any difference? and how do you determine the value?

enter image description here

(Image source: Circuits Today)

  • \$\begingroup\$ Can you not crop the screen grab? 80% is irrelevant. \$\endgroup\$ – Transistor Sep 29 '18 at 9:35
  • \$\begingroup\$ okay, I have cropped the photo. \$\endgroup\$ – Navaro Sep 29 '18 at 15:32

The inputs of an opamp have input bias currents. If one input is connected to 0V and the other input has R1 then the opamp will amplify the voltage produced by the input bias current in R1 a few hundred thousand times and cause the output of the opamp to latch at a voltage that is as high or as low as it can go.

You must balance the DC input voltages which might not be equal and might change when the temperature changes.

  • \$\begingroup\$ Some systems use auto-zero before every computation or signal-processing event, to avoid this type of error. \$\endgroup\$ – analogsystemsrf Sep 29 '18 at 2:52
  • \$\begingroup\$ can you explain how to choose its value? how does a auto-zero error system look like ? \$\endgroup\$ – Navaro Sep 29 '18 at 15:25

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