This function is a multiplier block with 2-to-N input ports. Individual
gains and offsets can be applied to each input and to the output. Each input
is added to its respective offset and then multiplied by its gain. The
results are multiplied along with the output gain and are added to the
output offset. This model operate in DC, AC and Transient analysis modes.
However, in AC analysis it is important to remember that results are invalid
unless only one input of the multiplier is connected to a node which bears
an AC signal (this is exemplified by the use of a multiplier to perform a
potentiometer function: one input is DC, the other carriers the AC signal).