Fully integrated LTE Doherty power amplifier

This paper demonstrates a fully integrated Doherty power amplifier for the LTE standard. The Doherty power amplifier is fully integrated adopting a 0.25 μm SiGe BiCMOS technology. The quarter wave transmission line is implemented by lumped element components to save chip area. By combining the phase compensation network with the input matching network of the peak amplifier, the required inductor number of the Doherty amplifier is reduced. Hence, the chip size is just 1.3 mm×1.8 mm. The fabricated power amplifier delivers an output power of 22.5 dBm with a power added efficiency (PAE) of 21%. For the complete 6 dB back-off region, the PAE is above 10%, and satisfies the EVM requirements for the QPSK and QAM16 modulation schemes for the 2.4 GHz LTE downlink with 20 MHz bandwidth. The measured results prove that the demonstrated Doherty amplifier is applicable for full integration with reduced chip size.