High-precision, Wide Bandwidth Cmos Fully Differential Operational Amplifier Technology Research

Based upon basic principles of the analog integrated circuit and theories of system stability, this paper deals with high precision, wide band-width and fully differential CMOS Operational Transconductance Amplifiers (OTA). Other than discussions about its performance evaluation and testing, a two-stage full differential OTA has also been designed including its core cell and the overall layout.Firstly, a two-stage structure for the OTA is presented after comprehensive considerations on characteristics like open-loop gain, unity-gain bandwidth, phase margin and settling time. Then the input and output topologies have been decided by comparing different structure available for this purpose.During the process of designing the core cell, a novel continuous common-mode feedback structure has been proposed, which is suitable for the input stage. In the meanwhile, according to the quite different demands which the overall performance of the OTA imposes on its input and output cells, utilizing characteristics of switched-capacitor and common-mode feedback circuit, continuous common-mode feedback method and switched-capacitor method have been applied to the input and output cells, respectively.At last, using the advanced EDA tool Cadence and SMIC 0.35μm CMOS process model, the typical circuit cells are simulated by HSPICE. The results show that the open-loop gain, unit-gain bandwidth, phase margin and settling time are 88dB, 612.2MHz, 48.4o, 4.52ns respectively, at the cost of a power dissipation of 14. 06mW. The module applies SMIC 0.35μm AMS CMOS 2P4M process,The final chip area consumption of the OTA circuit is 0.5*0.2mm~2.The results demonstrate that the high precision and wide bandwidth fully differential OTA satisfies, even exceeds, the parameters set beforehand. After slight modification, this circuit has been successfully applied to the MDAC, named switched-capacitor amplifier in 10-bit 100MSPS ADC. Moreover it can also be widely applied to vital circuit units in electronic fields like video receiving and data processing.