A 1-Henry inductor in the feedback loop (output to "op
amp" if direct, or feedback ladder to input if scaled) is
a convenient way to get a circuit that will solve at DC
but has a "broken" AC loop. Using a sinusoidal, zero DC
value current source and picking off the input difference
voltage with a vcvs, you can get your input mag & phase
for the plots (even though the values will not be unity
and zero, you can use the result, it's just explicit rather
than implicit and you will have to stuff the calculator by
hand rather than using the canned routines, perhaps).