A GaN voltage-mode class-D MMIC with improved overall efficiency for future RRH applications

This paper reports on a compact voltage-mode class-D power amplifier module suitable for the LTE frequency band of 800 MHz. It includes a 3-stage GaN MMIC and a hybrid lumped-element output filter network. For the MMIC PA novel design techniques have been applied. They lead to a significant improvement in power added efficiency (PAE) of the entire chip, which has been the major drawback of the voltage-mode class-D type of PA so far. The optimized amplifier achieves for a 50% duty-cycle pulse-width modulated input signal a maximum PAE of 59% at an output power of 5.2 W. Drain efficiency of the final stage stays almost constant over the whole output power range with values around 80%. To the authors' best knowledge these are record values in terms of PAE for this type of PA.