Chapter 12 encompassed different tubes to generate and amplify microwave energy. These tasks can also be performed by semiconductor devices which include different types of diodes and transistors. The tubes are suitable for higher powers, higher frequencies of operation, higher operating voltages and for higher degree of amplification linearity. On the contrary, the semiconductor devices have smaller size, lesser weight, low cost, higher reliability and greater energy efficiency particularly with CMOS technology. The highly automated manufacturing processes and easy availability of their complementary devices are the added advantages.