Abstract: A power amplifier design method for filtered matching networks is proposed. The method converts the high-order matching network into a low-order passive matching network with transistor parasitic output capacitance and parasitic package inductance, resulting in a more compact area. An ultra-wideband laterally diffused metal oxide semiconductor power amplifier is made to validate the proposed design process and confirm its viability. The test findings show that its drain efficiency is from 50% to 68% and that its output power ranges from 49.3 dBm to 50.9 dBm in the range of 300 MHz~900 MHz. Additionally, W-CDMA signals are used to test the circuit′s linearity index. The adjacent channel power ratio value for the entire bandwidth is below -43 dBc at 44 dBm output power, and it is still able to sustain about -30 dBc at 48 dBm output power. The experimental results demonstrate that the suggested network synthesis approach may satisfactorily achieve the performance indices in the design of an ultra-wideband power amplifier, resulting in a number of benefits in wideband design.