Design of a High-Order Continuous-Time Low-Pass Filter with a Novel Low Distortion Amplifier

Abstract

This paper presents a highly linear and high-speed operational-amplifier (OPAMP). The OPAMP consists of a double-recycling folded cascode (DRFC) input stage and an adaptive biasing with a flipped voltage follower to boost slew-rate (SR) and unity-gain frequency (UGF). In addition, frequency compensation is performed by an input cross-coupled phase-lead passive compensation scheme and hybrid Miller cascode compensation. A 56 MHz -3dB bandwidth fifth-order programmable gain continuous-time active low pass filter is fabricated in 180nm CMOS to validate the proposed scheme. The filter achieves 30.5 dBm of third-order interception point (IIP3) at 38MHz and occupies 0.215mm2. The filter consumes 14.7 mW with 1.8 V supply and has 0.2 dB in-band ripple.