A Fifth-Order 20-MHz Transistorized- -Ladder LPF With 58.2-dB SFDR, 68- Efficiency, and 0.13- Die Size in 90-nm CMOS

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-μW/pole/MHz favorably comparable with the state of the art. The die size is merely 0.13 mm².