5.6 Input Bias Current

In the ideal operational amplifier, no current flows into the inputs of the operational amplifier. However, due to internal leakage currents, a small amount of current flows into (or out of) the inputs. Expect this current to be in the nA to µA range, with the current increasing significantly as temperature goes up.

It is important that there is always a path for this current to flow. If the input is AC coupled or the signal source is not referenced to the ground of the microcontroller, this charge can build up and cause erroneous behavior. A method of diverting this current is shown below in Figure 5-4.