An 88% fractional bandwidth reconfigurable power amplifier for NB-IoT and LTE-M in 22 nm CMOS FDSOI

A wideband power amplifier (PA), with 88% fractional bandwidth operating in the 700 MHz to 1.8 GHz range, which covers most of the standardized narrowband internet-of-things (NB-IoT) and LTE-M bands, is fully integrated in 22 nm CMOS FDSOI. A single-stage differential amplifier core, combined with an on-chip balun, realizes a single-ended output. A stacked circuit architecture, with 3.3 V LDMOS transistors as output devices and thin-oxide flipped-well transistors as the input common-source (CS) stage, enable a wide bandwidth and reliable operation at a supply voltage of 2.55 V. Capacitor banks with stacked thin-oxide transistor switches tune the PA frequency characteristics over the wide frequency range. The PA delivers a saturated output power (P
sat
) of up to +24.4 dBm with up to 45% power-added efficiency, which is compliant with the current 3GPP standard for NB-IoT and LTE-M. The maximum power-gain varies between 30.7 dB and 29.2 dB over the whole frequency range. The PA core circuit occupies 0.32 mm
²
of silicon area, of which 0.2 mm
²
is occupied by the low loss balun.