This paper presents an input power-dependent high-efficiency LDMOS power amplifier by employing a dual-mode operation design approach. The proposed amplifier scheme provides two different operating modes depending on the power level: low or high input power modes. By controlling the number of operating amplifiers in each mode, the efficiency of the amplifier at low power level is substantially improved. Four single stage LDMOS power amplifiers with Motorola MRF 21030 were incorporated with a dual-mode input power divider and output power combiner. In the proposed operation, either one or four amplifiers were activated. The measurement results show a 50 dBm saturated output power and 40% PAE in high input power mode, when four amplifiers are active. By switching the operation to the low input mode, when the input power was relatively low, a 5% increase in PAE was obtained.