Design of low-voltage OTA for Sigma-Delta modulator
Lai Zhao-ze · Electronic Design Engineering · 2010
Operational Transconductance Amplifier is an important module in the analog circuit,which always determines the performance of the whole system.A low-voltage fully-differential folded-cascode OTA is designed for high-order Sigma Delta modulator in the paper.The OTA uses classic folded cascode structure.Auxiliary feedback amplifiers and the switched capacitor common mode feedback circuit are employed.The OTA is fabricated on SMIC 0.18μm CMOS mixed signal process.The simulation result of whole circuit in Spectre,shows that the open-loop DC gain is 72dB,the unity-gain bandwidth is 91.25MHz,the phase margin is 83.35°,the slew rate is 35.1V/μs at a driving load of 5pF,and the total power consumption of the device is only 1.41mW.A low-voltage supply 1.8V is adopted in the design,and the parameters of circuit are optimized to achieve well performance in this low-voltage supply.This amplifier is suitable to the application for high resolution Sigma Delta modulator.