A Fourth Order Elliptic Low-Pass Filter with Wide Range of Programmable Bandwidth, Using Four Identical Integrators

A new method to implement elliptic filter with identical integrators and no derivatives is presented. Using identical capacitor arrays as opposed to highly spread capacitor arrays of conventional implementation makes elliptic filter design with wide range of programmable/tunable bandwidths extremely simple, time-efficient and accurate. The proposed method also reduces the die size while realizing elliptic filter more faithfully. To demonstrate the method, a fourth order elliptic filter with nine programmable bandwidths ranging from 1.1 MHz to 17.6 MHz is designed. The 1.75 mm² filter draws 10 mA from 3.3 V supply at output swing of 4.0 V ppd in 0.35 um CMOS process to meet less than 50 nV radicHz in-band output-referred noise and SFDR of better than 80 dBc.