Progresses in the last five years have shown that CMOS can be a competitive technology also for RF transceivers, including those for applications with stringent requirements, such as cellular telephony. The prospect of a single-chip radio arouses considerable interest, even though it remains to be investigated whether it is either feasible or advantageous to put the RF front end on the same die as the rest of the mobile terminal. Even the less ambitious objective of implementing the mobile terminal with a set of separate chips in the same CMOS technology may bring considerable economic benefits, as this enables a company to rationalize the number of different technologies that have to be maintained for a given product. In this spirit, the feasibility of realizing efficient power amplifiers in regular CMOS is also beginning to attract increased attention.
In this project, a class-E power amplifier with finite DC-feed inductance has been implemented in a 0.25 um CMOS technology. A common-gate switching scheme has been employed which reduces the stress on the switching transistors. The amplifier achieves 41% power-added efficiency and 10 dB power gain while delivering 0.9 W to a 50 W load at 900 MHz