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This paper proposes a broadband asymmetrical monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) using 0.25-μm gallium-nitride process with a compact chip size of 2.37 × 1.86 mm2 for 5G communication. It adopts an unequal Wilkinson’s power divider with a ratio of 2.5:1, where 71.5% of the total power is transferred to the main amplifier for higher gain. Different input matching networks are used to offset phase difference while completing impedance conversion. This design also applies a novel topology to solve the problem of large impedance transformer ratio (ITR) in conventional DPA, and it optimizes the ITR from 4:1 to 2:1 for wider band. Moreover, most of the components of the DPA including power divider and matching networks use lumped inductors and capacitors instead of long transmission line (TL) for a smaller space area. The whole circuit is designed and simulated using Agilent’s advanced design system (ADS). The simulated small-signal gain of DPA is 8–11 dB and the saturation output power is more than 39.5 dBm with 800 MHz band from 4.5 GHz to 5.3 GHz. At 6-dB output power back-off, the DPA demonstrates 38–41.3% power added efficiency (PAE), whereas 44–54% PAE is achieved at saturation power.

This article proposes a parallel dual‐metal‐gate structure (PDM) of AlGaN/GaN high‐electron‐mobility transistors (HEMTs) for high‐linearity applications. Cancellation of the third‐order derivative of the curve (is achieved by splitting the device into two subcells in parallel with different gate metals. The two subcells have different threshold voltages. When the same bias voltage is applied, the operating states of the two subcells are independently controlled by the gate bias voltages. The maximum transconductance () of the conventional single‐metal‐gate (SMG) HEMT, double‐metal‐gate (DMG) HEMT, and PDM‐HEMT is all comparable, whereas of the proposed structure is 75% lower than that of the SMG HEMT and 47.8% lower than that of the DMG HEMT. The effects of the differences and width ratios of the work function on are studied and compared, and a suitably designed PDM‐HEMT that can considerably improve linearity without degrading other performance aspects is obtained. This research has significant implications for high‐linearity applications.