Answer 2—In an inverting amplifier, both of the opamp’s inputs are held at an essentially constant value, which means that the operating point of the input differential amplifier doesn’t change. Both the gain and the input bias current of this stage remain essentially constant.

In a noninverting amplifier, there is a significant common-mode voltage swing at the op-amp’s inputs. If this is a large fraction of the supply voltage, there can be significant changes in gain, offset voltage, and input bias current, particularly in op-amps that have rail-to-rail input capability. This can present additional challenges to the circuit designer when pushing the performance limits of the op-amp.

Contributor: David Tweed