Since for each
, a nonminimum phase

zero contributes an additional phase lag and imposes limitations on the rolloff rate of the
open-loop gain. For example, suppose *L* has a zero at *z*>0; then

Since the slope *L*of near the
crossover frequency is, in general, no greater than -1, which means that the phase due to the minimum phase part, *L*mp, of *L* will, in general, be no greater than -90o, the crossover frequency(or the closed-loop bandwidth) must satisfy