Continuous-time delta-sigma modulator with an upfront passive-RC low-pass network

Abstract

A power-efficient third-order single-bit continuous-time Delta-Sigma modulator (CTDSM) with an upfront low-pass network (LPN) is presented. The passive LPN functions as an adder and a filter that realizes a noise transfer function zero and reduces the signal swing at the input of the subsequent active integrator. Transistor-level simulation results in 0.18μm CMOS show that the proposed CTDSM achieves 71.1-dB SNDR over a bandwidth of 2 MHz with a sampling frequency of 256 MHz, while consuming 124.5 μW power from a 1.8-V supply.