This paper presents a buck converter with Type-III compensation and a transient enhanced transistor (TET) for portable devices. A large power inductor value is desirable in DCDC conversion for reducing the inductor current ripple, and consequently improving the efficiency. However, the main limitation of the load transient response is the large power consumed by the inductor. In this work, we place a TET in parallel with the main power inductor. The transient control circuit detects the load transient from the error amplifier output, and controls the TET to charge or discharge the output. The proposed buck converter, designed in 180-nm CMOS, operates at 10-MHz and reaches a simulated 95.2% peak efficiency over a load range of 0.1A to 1.5A, at 1.8V of output voltage. When compared with the conventional buck converter, the proposed architecture reduces the settling time from 9.3μs to 3.4μs and the undershoot voltage from 420mV to 214mV, during a load change from 0.1A to 1.35A. Besides, it decreases the settling time from 10.4μs to 3.1μs and the overshoot voltage from 350mV to 58 mV, during a load change from 1.35A to 0.1A.