Analysis and design of an unconditionally stable common-drain class-B RF power amplifier in 90 nm CMOS technology

Modern communication networks demand power amplifiers (PAs) which are efficient and have low distortion. The common drain amplifier has the potential to become a linear amplifier with good efficiency, when biased at or above class-B. The main challenge is to provide unconditional stability while still maintaining adequate transducer gain so that the power added efficiency (PAE) will not be compromised by low gain and, thus, resulting in better overall performance. In this contribution, analysis and design of an unconditionally stable common drain class-B PA for the LTE band at 2.55 GHz in 90 nm CMOS is presented. The simulation results show that the designed PA can deliver an output power of more than 27.2 dBm with gain of 6.1 dB and PAE greater than 43.0 % when operated from 2.5 V supply. The circuit has a third order intermodulation distrotion suppression of 32.0 dBc at 3 dB input back-off.