Abstract: An RF power amplifier for amplifying an RF signal over a broad range of power with improved efficiency includes a main amplifier for amplifying an RF signal over a first range of power and with a power saturation level below the maximum of the broad range of power. A plurality of auxiliary amplifiers are connected in parallel with the main amplifier with each of the auxiliary amplifiers being biased to sequentially provide an amplified output signal after the main amplifier approaches saturation. The input signal is applied through a signal splitter to the main amplifier and the plurality of auxiliary amplifiers, and an output for receiving amplified output signals from the main amplifier and the plurality of auxiliary amplifiers includes a resistive load R/2. The split input signal is applied through a 90° transformer to the main amplifier, and the outputs of the auxiliary amplifiers are applied through 90° transformers to a output load.

Abstract: A semiconductor device is fabricated in a silicon on insulator (SOI) substrate including a supporting silicon substrate, a silicon oxide layer supported by the substrate, and a silicon layer overlying the silicon oxide layer. An electrical component is fabricated in the silicon layer over a portion of the silicon oxide layer, and then the substrate opposite from the component is masked and etched. A metal layer is then formed in the portion of the substrate which has been removed by etching with the metal layer providing heat removal from the component. In an alternative embodiment, the silicon oxide layer overlying the portion of the substrate is removed with the metal layer abutting the silicon layer. In fabricating the device, preferential etching is employed to remove the silicon in the substrate with the silicon oxide functioning as an etchant stop. A two step process can be employed including a first oxide etch to etch the bulk of the silicon and then a more selective but slower etch.

Abstract: The power delivered by an RF power transistor having cascaded cells or unit elements is improved by reducing the phase imbalance between elements and thereby reducing transverse effects between cells. Phase imbalance is reduced by varying the number of transistor elements connected to interconnect areas, connecting wire bonds to an input transmission line concentrated near an outer edge in the transmission line to take advantage of surface skin effects on current, and varying the surface area of the interconnect areas to adjust input impedance and output impedance of each cell.