Bandwidth vs. Efficiency Trades in RF Amplifier Design
Mobile communications systems continue to expand operation over wider frequency bands, while striving to extend battery life. The main bottleneck to achieving the goals of increased bandwidth and efficiency continues to be the RF power amplifier. Many factors influence an amplifier's bandwidth and efficiency. However, it is not obvious how the various design variables work to restrict an amplifier's efficiency based on certain bandwidth requirements or vice versa. This paper describes the major design tradeoffs in some detail.
This paper examines the various design variables that work to limit a power amplifier's bandwidth and efficiency, specifically how each requirement restricts the other. Various amplifier technologies, topologies, and design techniques are presented and discussed along with their pros and cons. Analysis into the fundamental restrictions on bandwidth and efficiency for different amplifier classes and topologies is also presented along with results of specific cases. Finally, summary spreadsheets are presented that illustrate the bandwidth verses efficiency tradeoffs based on several devices currently available on the market.