Full Differential Operational Transconductance Amplifier for High Order Sigma Delta Modulator
Weidong Wang · Dianzi qijian · 2009
By comparing three kinds of operational amplifiers with telescopic casocde,fold-cascode and two states class AB output structure,a full differential operartional transconductance amplifier was proposed,which can be used to high order feed fordward Sigma Delta modulator.The two stages class AB output structure with the CMFB circuit was designed with SMIC 0.18μm CMOS technology.The simulation results in CADENCE/Spectre showed that the DC gain of the amplifier is 62.19 dB,and the unity-gain bandwidth is 205.56MHz.The phase margin is 70.81°and power dissipation is only 0.42mW,which is suited for low voltage/low Sigma Delta Modulaor.