A 2.4-GHz 0.82-mW Hybrid Balun for Low-Power Fully-Differential Direct Conversion Receivers in 0.18 μm CMOS

A low-power, low-noise, highly-linear hybrid balun circuit is proposed for fully-differential low-power CMOS RF receivers. The hybrid balun is composed of a passive transformer and loss-compensating auxiliary amplifiers. Design issues regarding the optimal signal splitting and coupling between the transformer and compensating amplifiers are discussed. Implemented in 0.18-mum CMOS, the 2.4-GHz hybrid balun achieves 2.8-dB higher gain and 1.9-dB lower noise figure than its passive counterpart and +23 dBm of IIP3 only at a current consumption of 0.67-mA from 1.2-V supply. It is also examined that the hybrid balun remarkably lower the total noise figure of a 2.4-GHz fully differential RF receiver only at a cost of 0.82-mW additional power dissipation.