Alternative m-derived termination for distributed amplifiers

Use of the bisected-T m-derived filter section at the input and output of distributed amplifiers is a widely known technique to improve matching and gain flatness near the amplifier cutoff frequency. We propose the use of the new bisected-pi section to achieve larger gain, lower noise figure, and smaller area for the same bandwidth and matching characteristics. We show the theoretical basis for the improvement and confirm the result by comparing two otherwise identical distributed amplifiers in 130 nm CMOS. We measured a gain increase of approximately 1.2 dB and a noise figure reduction over the entire bandwidth of the amplifier. Additionally, the new topology uses fewer unique inductor sizes and smaller total inductor area to give reduced design time and cost. The pi-based approach should become the new standard for integrated distributed amplifier design.