Conference, Paris, 17-20, March 1997

A methodology for analysis and synthesis of lowpass sigma-delta (SD) converters is presented in this paper. This method permits the synthesis of SD modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of continuous-time model and using a discrete simulator which is more efficient than an analog simulator. Finally, a realistic design of a second-order SD modulator with a compensation of the non ideal behavior of DAC is given. Moreover, simulation results show a good agreement with the theoretical bases. 1. Introduction Sigma-delta (SD) circuits are very attractive analog-todigital converters because they achieve high accuracy with few critical analog components [1]-[2]. They are composed of a SD modulator which provides a high speed one bit data string followed by a digital filter and decimator to produce a high resolution data. The lowpass SD modulator consists of one or more integrator and a one bit quantize..