Op Amp input impedance vs. attenuation

[juz_ad]

The config on the left has an an output that is approx. unity and an input Z of approx. 100K (set by R2).

The config on the right has an output that is attenuated by a factor of 100:1 - but (according to what I've been told...) also has an input Z of approx. 100K.

I understand the difference between the 2 R voltage dividers (1:100 and 100:1) - but how is the input Z the same for both configs?

Thanks.

 

[WimRFP]

A unity gain inverter has very high input impedance (because there is virtually no voltage across input terminals of opamp). You should think of many MOhms (of course depending on frequency of operation).

So your source is right, both circuits have same input impedance.

 

[LvW]

So your source is right, both circuits have same input impedance.

... because - in both cases - R1 and R2 are connected in series.