Author : Yogita Gajare 1
Date of Publication :16th September 2021
Abstract: Wireless terminals with higher capacity and data rates, indicating a new advancement in wireless transceivers. Sigma delta ADC is one of the most used devices in these wireless services. In this work, sample design of 1st order switched capacitor sigma delta modulator is highlighted for CDMA (Code Division Multiple Access). This paper introduces a modified OTA (Operational Transconductance Amplifier) design technique for balancing GBW (unity Gain Bandwidth) and Stability in switched capacitor sigma delta modulators for high frequency applications. For high frequency applications, adjusting the degree of stability with other parameters like as GBW, Slew Rate, and so on is a difficult process. As a result, instead of using separate biasing scheme in the existing method, a voltage divider scheme is used to bias miller series transistors, tail transistors of differential amplifiers, and transistors of output source stage amplifiers all at the same time. In addition, behavioral modelling of a 1st order switched capacitor sigma delta modulator is performed to design OTA for all non-idealities. The effectiveness of the suggested OTA is confirmed by simulation results of a 1st order switched capacitor sigma delta modulator in Cadence Virtuoso utilizing AMS 180nm CMOS technology
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