Several broadband medium-power millimeter-wave power amplifiers (mm-Wave PAs) are designed using GlobalFoundries' 22-nm fully-depleted silicon on insulator (FD-SOI) CMOS technology. A fixed-biased PA is designed, which achieves max. power-added-efficiency (PAE) = 36.7%, PAE@P1dB = 14.1%, and PSAT of 17.2 dBm at 24 GHz according to post-layout parasitics extracted (PEX) simulations. An adaptive biasing circuit is then added to the fixed-bias PA to improve PAE at power backoff, where it achieves similar performance in PEX simulations in bandwidth (BW), max. PAE, P1dB, and PSAT; however, its PAE@P1dB is greatly improved to 29.2%. PAE@P1dB is improved across the full 20 - 40 GHz frequency band. In addition, two different ESD protection designs are studied to investigate the degradation of PA performance due to ESD diodes. With absolute 3-dB BW of ~80%, high max. PAE and PAE@P1dB, and the smallest PA core size compared with literature, the adaptive biased CMOS PA may be attractive for multiband mm-Wave 5G and other broadband mm-Wave applications.