A 76-dB-DR 6.8-mW 20-MHz bandwidth CT ΔΣ ADC with a high-linearity Gm-C filter

Abstract

A continuous-time ΔΣ ADC with a new high-linearity Gm-cell is presented. A loop filter employing a Gm-C filter is preferable to an active-RC filter with op-amps for low power consumption and a large phase margin. However, distortion caused by the Gm-cell degrades the ADC performance. A cascoded flipped voltage follower Gm-cell is proposed in order to address this problem. Simulation results reveal that the IIP3 of the proposed Gm-cell is 8 dB higher than that of the conventional Gm-cell. The 20-MHz bandwidth continuous-time ΔΣ ADC employing the proposed Gm-cell achieves 75.8dB DR, 72.4 dB SNDR and 49.9 fJ/conversion-step FoM with 6.8mW power consumption.