A Highly Linear Hybrid Class-F/J Filtering Power Amplifier Utilizing Bias Current Boosting Technique in InGaP/GaAs HBT Process

This paper presents a broadband high-efficiency and good-linearity power amplifier for L-band applications in a 2-μm InGaP/GaAs heterojunction bipolar transistor (HBT) process. An off-chip lumped-element harmonics-tuned output matching circuit, combining the core of Class-F and Class-J configuration, is designed on a 4-metal-layer laminate with a total size of 3 × 3 mm
²
to promote the efficiency. A linearization technique of an improved adaptive bias circuit with extra DC path is analyzed. At the state of saturation, this structure enables the transistors biased in Class-AB to switch to Class-A, boosting the bias current and stabilizing the base bias voltage. The simulation results of the PA show a 32.3-dBm linear output power with a phase distortion of only 5.5° is obtained, and the power added efficiency (PAE) at output power 1-dB compression point (OP1dB) is better than 42% within the frequency range of 1.6-2.1 GHz.