This function is a two-quadrant divider. It takes two inputs; num
(numerator) and den (denominator). Divide offsets its inputs, multiplies
them by their respective gains, divides the results, multiplies the quotient
by the output gain, and offsets the result. The denominator is limited to a
value above zero via a user specified lower limit. This limit is approached
through a quadratic smoothing function, the domain of which may be specified
as a fraction of the lower limit value, or as an absolute value. This model
will 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 divider is connected to a node which bears an AC signal (this is
exemplified by the use of the divider to perform a potentiometer function:
one input is DC, the other carriers the AC signal).