Solid State Device Technology is ubiquitous in communications, radar, and EW applications. This presentation will cover Si LDMOS, PHEMT, InP HEMT/MHEMT and GaN HEMT. Content includes principles, classes, and state of the art benchmarks. The art of power amplifier design is approached from a historical perspective. Power amplifiers utilizing these device technologies covering UHF through sub-millimeter wave are described. Future trends are highlighted and summarized.