A 40W ultra broadband LDMOS power amplifier

An ultra-broadband power amplifier using a Freescale 50V LDMOS device is presented. The power amplifier can deliver 40W PEP power from 2 to 800 MHz with better than 30dBc IM3 at 10 kHz 2-tone spacing. The power gain is 19 dB with ± 1 dB gain flatness across the band at class A operation and 15 dB ± 1 dB gain flatness at class AB configuration, each with a 36 V supply voltage. The drain efficiency is better than 30% from 2 MHz to 1 GHz. The impedance matching technique utilizes a two-section broadband balun impedance transformer with ferrite beads which allow the device to operate at low frequency down to 2MHz, and a series R-C feedback loop to improve the gain flatness. The broadband matching methodology based on the non-linear model is introduced as well.