In this paper, we present on-chip frequency compensation with a capacitor multiplier for a current-mode control DC–DC converter. The capacitor multiplier technique can effectively remove the crossover frequency from the origin. An equivalent capacitance is obtained by amplifying the small current in the capacitor. The value of the equivalent capacitor can be adjusted. The functional block diagram and small-signal transfer function of a buck DC–DC converter are derived for a simplified system loop for on-chip frequency compensation with a capacitor multiplier. In this paper, the derived system transfer function for frequency compensation is verified by simulation and from test results. The proposed circuit is suitable for low-cost and small-size applications. Simulation results and experimental results are presented to demonstrate the theoretical analysis.