A 33-MHz 70dB-SNR super-source-follower-based low-pass analog filter

Abstract

In this paper a 4th-order low-pass continuous-time analog filter is presented. A smart and compact biquadratic cell has been realized using the super-source-follower circuit. The biquadratic cell synthesizes a 2nd-order low-pass transfer function, using only two capacitors and four transistors per stage: two transistors for gm-C transfer function and two transistors as current sources for biasing purpose. A 4th-order filter prototype has been integrated in CMOS 0.18μm technological node. The achieved Signal-to-Noise-Ratio is 70dB, with 8nV/√Hz in-band input referred noise. In-Band IIP3 is 18dBm. The current consumption for the entire 4th-order filter is 770μA, from a single 1.8V supply voltage.