A 1.2-V 90-nm Fully Integrated Compact CMOS Linear Power Amplifier Using the Coupled L-Shape Concentric Vortical Transformer

This paper presents a 90-nm fully integrated CMOS linear power amplifier (PA) using a coupled L-shape concentric vortical transformer (CL-CVT) for the fourth-generation long-term evolution (LTE) communication standard. Using the proposed output combining CL-CVT architecture, the outer diameter required by the power combiner is reduced by 66% compared to the distributed active transformer with similar performance. Moreover, the PA is able to efficiently combine four push-pull output stages and achieve nearly constant power over several LTE bands with a total chip area less than 1 mm². With a 1.2-V supply voltage, the PA delivers 27.3-dBm maximum output power with a peak drain efficiency of 47% at 2.4 GHz. Using a 20-MHz LTE 16-QAM test signal, the PA achieves 24.6% power-added efficiency at an output power level of 22 dBm and passes the spectral requirements defined by the LTE standard without using any pre-distortion or calibration techniques.