something I commonly see in schematics which include op-amps set up as inverting amplifiers is the inclusion of a resistor between the non-inverting "(+)" input of an op-amp and a strong voltage reference such as ground, power, or a voltage reference set up using an op-amp buffer.
What is the purpose for this? The (+) input of op-amps are high impedance, and the references mentioned above are strong sources of current, which aren't vulnerable to crosstalk in the way a weak reference would be.
Best Answer
Figure 1. Both op-amp inputs have a bias current. If R3 is zero ohms then there will be a difference in the offsets between the two inputs. Source: ECircuitCenter.
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