Extended Continuous Inverse Class-F Power Amplifiers With Class-AB Bias Conditions

In this letter, the operation of continuous inverse Class-F (Class-F⁻¹) mode with Class-AB bias conditions is modeled. The extended waveform expression of intrinsic drain current is derived for continuous Class-F⁻¹ power amplifiers (PAs) biased above pinchoff point. Based on the modified current and voltage waveform formulas, the delivered power and efficiency performance is analyzed as a function of conduction angle. Moreover, the design space of fundamental and harmonic load admittances is generalized for any conduction angle between <inline-formula> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula>. For experimental verification, a broadband PA is implemented with a 6-W LDMOS device. Under a Class-AB bias condition, the fabricated PA exhibits more than 70% power added efficiency and 38-dBm output power with a fractional bandwidth of 62% from 500 to 950 MHz.