Stacked Si MOSFET strategies for microwave and Mm-wave power amplifiers

In order to increase voltage handling capability of Si digital FETs in power amplifier circuits, an increasingly popular strategy is to use series connections of multiple devices which share the same drain current. This approach has led to amplifiers at cell-phone frequencies that achieve watt-level output powers with good efficiency, linearity and extended bandwidth. It has also been shown to work effectively at mm-wave frequencies up to 90GHz, and in wideband amplifiers with bandwidths up to 50GHz. This presentation reviews progress and challenges of the stacked MOSFET approach. Issues associated with maintaining proper alignment of current and voltage as one moves up through the stack are highlighted.