This paper describes a software-defined-radio (SDR) balun low-noise amplifier (LNA) with no explicit bias circuit, inductor or ac-coupling network. It relies on a triple-stage inverter-based amplifier with resistive feedback to maximize the bandwidth and realize single-to-differential conversion. RC degeneration applied at the last gain stage enhances both linearity and output gain-phase balancing. Optimized in 65-nm CMOS the balun-LNA covers the 0.02-to-6-GHz band with S >11 dB, voltage gain of 21.2-dB and noise figure below 3.2-dB. The in-band IIP2 (IIP3) is +36 to +51 dBm (5.6 to 5.3 dBm). The power consumption is 7.9 mW at 1.2 V. © 2012 IEEE.