Journals Proceedings

Abstract

In this paper SIMSIDES-based behavioral simulation of a 4th order Hybrid ΣΔ (HΣΔ) modulator was carried out to define electrical characteristics of an Analog Building Block (ABB), specifically a fully differential OTA. A set of experiments based on analytical models was defined to analyze the overall performance of the Switched Capacitor (SC) ΣΔ modulator in order to translate the design considerations into a set of values that the design at transistor level can be established by the desired performance of the chosen architecture. In accordance with this design strategy, a fully differential CFCFC OTA was designed according to design rules of a 130nm CMOS process. Simulation results show that an open-loop gain A0 = 60dB, and unity-gain bandwidth f0dB = 1.0GHz are enough to obtain a Signal-to-Noise Ratio (SNR) of 68dB (±1dB) when this OTA is added to the DT ΣΔ modulator. Furthermore the hand-made small-signal analysis of the chosen OTA topology allow us to obtain an analytic design model useful to correlate not only CADENCE results, but also to identify the most important parameters affecting the frequency response