A 5W ultra-broadband power amplifier using silicon LDMOSFETs

We present the design of a high-efficiency power amplifier using silicon LDMOSFETs for the ultra-broadband from 2 to 500 MHz. To achieve both the high efficiency and the output power required, the bias condition for the class-AB operation has been applied. In addition, a push-pull structure and a negative feedback network have been adopted for the broadband operation which has been implemented using broadband coaxial transmission line transformers and a broadband high-Q RF choke inductor. It is shown from the experimental results presented that the implemented power amplifier exhibits an output power at the 1dB compression point (P1dB) of more than 5 W, as well as having a power-added efficiency of more than 43% at P1dB over the entire operational frequency band from 2 to 500 MHz. The results also show very flat power gain characteristics of 22±1.5dB from 2 MHz to 500 MHz.