Design and Analysis of a Stage-Scaled Distributed Power Amplifier

This paper presents the design, analysis, and measurement of a pseudodifferential distributed power amplifier in a 0.13-μm SiGe BiCMOS process. To mitigate the large loaded transmission line loss due to bipolar base resistance, emitter degeneration is used and an optimal small-signal design point is selected for maximum gain-bandwidth product. To enhance the efficiency of distributed amplifiers (DAs), a stage-scaling technique is proposed to utilize more voltage swing while reducing the total current consumption. The output power and efficiency of the amplifier are evaluated as a function of two scaling coefficients. The fabricated distributed power amplifier achieves a small-signal gain of 10 dB and a 3-dB bandwidth of 110 GHz. The measured midband saturated output power is 17.5 dBm with a peak power-added efficiency (PAE) of 13.2% and the 3-dB output power bandwidth is greater than 77 GHz. The amplifier consumes 119 mA from a 3-V supply and occupies an area of 2.08 mm × 1.05 mm. Compared to a uniform nonscaled DA fabricated in the same process, the stage-scaled amplifier achieves the same output power with higher collector efficiency and PAE over the entire measured frequency range.