A compact low-power 2.4-GHz ZigBee/wireless personal area network receiver is reported. It optimizes passive pre-gain with an inverter-based split low-noise transconductance amplifier (split-LNTA) to avoid the RF balun and its associated insertion loss, while enabling isolated in-phase (I)/quadrature (Q) passive mixing. The latter essentially saves power as a 50%-duty-cycle local oscillator (50% LO) can be generated more efficiently than its 25% counterpart. Specifically, a 2.4-GHz LC voltage-controlled oscillator (VCO) followed by an input-impedance-boosted Type-II RC-CR network produces the desired 50% four-phase LO with optimized power, I/Q accuracy, and phase noise. We also analytically compare the proposed "split-LNTA + 50% LO" architecture with the existing "single-LNTA + 25% LO," identifying their distinct features under current- and voltage-mode operations. The receiver fabricated in 65-nm CMOS exhibits 32-dB voltage gain, 8.8-dB noise figure (NF) and -7 out-band input-referred third-order intercept point that correspond to 59.4-dB spurious-free dynamic range. The VCO measures -111.4 phase noise at 3.5-MHz offset. The achieved power (1.4 mW) and area (0.14 mm2) efficiencies are favorably comparable with the state-of-the-art. © 1963-2012 IEEE.