# A Review of Advanced CMOS RF Power Amplifier Architecture Trends for Low Power 5G Wireless Networks
## 4 Conclusions  
Modern wireless systems comprise of different output power transmitters and a high number of users supporting radio access nodes. As a result, a traditional wireless network configuration morphs into a heterogeneous architecture. Even though wireless transceivers can be fully implemented using _III-V_ group semiconductors, the low level of integration and small digital capabilities of these technologies leads to a high price to functionality ratio; hence _III-V_-based technologies are not suitable for portable low power cells. CMOS, on the other hand, is scalable and provides a high level of integration for both analog and digital circuits at a reasonable (compared to that of _III-V_ group semiconductors) price. Due to low breakdown voltage, CMOS is not suitable for high power applications, but is perfect for low power transceiver blocks, including low power RF PAs.  
Classic linear RF PA architecture exhibits high levels of linearity but lacks efficiency (5-20%). Due to an increase in modern wireless network capacity, RF PAs with higher levels of efficiency without sacrificing linearity are required.  
Based on the review presented in this article, DPA and variations of ET/EER PA are the best candidates for the low- and high-frequency 5G range mobile applications implemented in CMOS process. Not all variations of ET/EER PAs are suitable for 5G due to the wide intermediate frequency requirements, and therefore adaptive bias, adaptive (multimode) supply-based implementation might be the most attractive approaches. A parallel combination of linear and switching regulators could also be an architecture worthy of consideration. A combination of a TWA and measures to increase the _PAE_, like the adaptive bias or supply from the ET/EER architecture, could provide a solution for low power wireless CMOS devices that might need to be compatible with multiple standards across different bands including the 5G realm. Even though the 5G mm-wave region is not best suited for CMOS PAs, DPA architecture and nonlinear classic PA arrangements are currently maturing in deep nanometer CMOS processes.  
All authors contributed to the present paper with the same effort in finding available literature resources, as well as writing the paper.  
This research was funded by the Research Council of Lithuania grant number DOTSUT-235, No. 01.2.2-LMT-K-718-01-0054 as a part of \"Design and Research of Internet of Things (IoT) Framework Model and Tools for Intelligent Transport Systems\" project. The article processing charges (APC) were funded by Vilnius Gediminas technical university Faculty of Electronics.  
The authors would like to thank the Research Council of Lithuania for providing PhD students with annual research scholarships, as well as [PERSON] for observations while writing this paper. The authors would also like to thank the Research Council of Lithuania and the whole project \"Design and Research of Internet of Things (IoT) Framework Model and Tools for Intelligent Transport Systems\" team for their support.  
The authors declare no conflict of interest.