Multistage Lossy Distributed Amplifiers

This chapter presents a new idea that is to optimize the lossy junctions as part of the optimization of the equalizers used in a multistage amplifier. The lossy junctions are introduced between lossless unit elements (UEs) composing an equalizer so that the equalizers can be used to offset power gain issues at low frequencies. In this resistive matching case, the real frequency technique (RFT) is used to directly synthesize the resistors and the UEs to satisfy both gain flatness and stability. The distributed multistage amplifier RFT is successfully modified to introduce the lossy elements and incorporated into a CAD program called SYNTARD. The chapter first validates the new concept by designing a single-stage 0.1-5 GHz microwave amplifier. Then, it uses the modified multistage RFT to design a two-stage 0.1-9 GHz broadband amplifier. In order to realize the equalizers, the chapter gives a lossy UE network synthesis method.