OP-AMP free SC biquad LPF and delta-sigma ADC

by Yoo, Kiseok

The objective of this work is to explore the feasibility of replacing

conventional op-amps with inverters in switched-capacitor (SC) circuits. In order to

verify the idea, a low-pass filter (LPF) and a second-order delta-sigma (??) analog-todigital

converter (ADC) are designed in the 0.5-?m CMOS technology. The low-pass

filter structure is based on biquad sections, and the ?? ADC system is based on a lowdistortion

modulator topology. The feasibility of the proposed idea is demonstrated

with system and circuit level.