Fun with resistors

[Zero999]

I haven't installed/used the software yet.

There's an error in the PDF file posted. It talks about Rsum being the load presented to the source on an inverting and non-inverting amplifier which isn't true. With the inverting amplifier, the input resistor determines the load seen by the source and the feedback resistor, the load seen by the op-amp's output stage in parallel with the load. With the non-inverting amplifier Rsum determines the load connected the op-amp's output stage, in parallel with the load.