A novel transistorized-$LC$-ladder low-pass filter (LPF) is realized by combining source followers with $Q$-enhanced floating differential active inductors. It features a small number of active devices to minimize the sources of nonlinearity and noise and a robust frequency response against process variations and device mismatches. A fifth-order 20-MHz LPF prototype is fabricated in 90-nm CMOS. It measures a 58.2-dB spurious-free dynamic range with 6.8 mW of power, which corresponds to a selectivity efficiency of 68-$\mu \hbox{W}/\hbox{pole}/\hbox{MHz}$ favorably comparable with the state of the art. The die size is merely 0.13 $\hbox{mm}^{2}$.