What is the idea behind this circuit? Inverting Op-Amp Current
Source Ideas: Keeping a constant current by adding a voltage
(removing voltage by an "antivoltage", helping the input voltage
source, zeroing resistance) In the simple current source the
voltage drop VL across the load affects the current. We have
already solved this problem by varying the internal resistance
and the excitation voltage. Let's now look for another remedy.
What do we do in our routine when an obstacle stands in our way?
We just remove it by an equal useful "antidisturbance"!
Following this powerful idea, we may compensate the harmful
voltage VL with an equival "antivoltage" -VL. For this purpose,
we have just to connect an additional supplementary voltage
source Bs in series with the load and adjust its voltage -Vs =
VL. As a result, the total excitation voltage V is constantly
applied across the resistor R and a steady current I = V/R flows
through the load. If we draw the additional supplementary
voltage source Bs under the main s