  We report on an all-optical magnetometric technique based on nonlinear
magneto-optical rotation with amplitude-modulated light. The method enables
sensitive magnetic-field measurements in a broad dynamic range. We demonstrate
the sensitivity of $4.3\times10^{-9}$ G/$\sqrt{\text{Hz}}$ at 10 mG and the
magnetic field tracking in a range of 40 mG. The fundamental limits of the
method sensitivity and factors determining current performance of the
magnetometer are discussed.
