I've heard of differential voltages, but the concept of a differential impedance is new to me.
Suppose we are trying to calculate/derive the differential input impedance of the following difference amplifier:
Then what would that mean and how would we go about that?
Pages such as this give information about the impedance seen at the inverting and non inverting inputs to the op-amp but they make no mention of the differential impedance, which leaves me stuck looking for answers. This post is very similar and gives us the answer R1 + R2 (which in our case is really R1 + R3), but there is no explanation of how we arise at that result, and this is where 'im stuck.
Thank you for any help and have a nice day.