This paper proposes a modified Doherty power amplifier (DPA) configuration for bandwidth and efficiency operations. To mitigate the efficiency degradation resulting from the incomplete load modulation network (LMN) and the knee voltage effect, the carrier transistor’s optimum load impedances based on related constant voltage standing wave ratio (VSWR) circle theory are introduced. Meanwhile, a innovative LMN with broadband matching technologies is adopted, which plays a guiding role on the bandwidth expansion from the theoretical point of view. In order to verify the practical feasibility of the design scheme, two 10W GaN HEMT transistors are used to design a broadband DPA. The measurement results show that the working bandwidth of the power amplifier is from 1.6 GHz to 2.6 GHz. The saturated output power of the whole frequency band is about 41.7–44 dBm and the drain efficiency (DE) is more than 50.8% at the input power of 33 dBm. In addition, the DE is 41.5–45% at 6-dB back-off power. Measurement results verify that the proposed enhancement techniques of bandwidth and efficiency are effective for DPA.