28 GHz >250 mW CMOS Power Amplifier Using Multigate-Cell Design

We report a mm-wave power amplifier IC that operates over the 25 - 35 GHz band and achieves saturated output power of more than 250 mW and peak PAE of 29%. The IC is implemented with 45-nm CMOS SOI technology and employs transistor stacking to achieve high operating voltage and power, and demonstrates a novel multigate-cell technique to implement FET stacking for mmwave applications. Unit cells are defined with a single transistor (one source and one drain) with 4 gate connections of 1.2 μm width each. External gate capacitances appropriate for the desired voltage division along the transistor are implemented within the unit cell itself using the metal stack available in the CMOS technology. The unit cell can be replicated in straightforward fashion to implement larger effective gate widths. In this work, an aggregate width of 307 μm is used, with simple input and output matching, to provide an amplifier centered at 28 GHz. To the authors´ knowledge, the output power is the best reported in silicon for this frequency range, for amplifiers that do not use elaborate power-combining approaches.