Design Of Low Flicker Noise,Low Offset CMOS Operational Amplifier

The semiconductor industry has developed rapidly for more than half a century.Analog integrated circuits have played an indispensable role in this,and operational amplifiers are the most important basic unit of analog integrated circuits.In recent years,with the continuous development of the information industry such as the Internet of Things,5G communications,artificial intelligence,and portable equipment,the importance of radar radio frequency transceiver chips as a bridge to the outside world has become increasingly significant.As a very important part of the receiver,the operational amplifier needs to amplify and detect the weak echo signal,so that the research of low noise and low offset operational amplifier has important practical significance.Based on this background,this paper focuses on the analysis of low noise and low offset CMOS operational amplifier design methods.The paper first introduces the theoretical basis of noise and offset in CMOS circuits,and analyzes the noise and offset in each basic circuit.Then on this basis,the paper focuses on the main circuit and design method of the operational amplifier.The bias circuit uses a simple structure and a powerindependent current reference to provide stable current.The input stage uses a folded cascode structure to provide larger gain and output swing.The output stage uses CLASS A structure to stabilize the signal with low distortion.Then the frequency compensation and CMFB are performed in the main operational amplifier to meet the phase margin and CMRR.Based on the design of the op amp,chopping technology and auto-zero technology are used to design the two amplifiers.The operational amplifier designed in 0.18 um CMOS technology,the simulation tool uses the spectre simulator in cadence,and the layout is also cadence.The simulation results are 101 dB open-loop gain,226 dB CMRR,and 86 dB PSRR.The equivalent input noise of the chopper amplifier at 10 Hz is 16.27nV/sqrt(Hz)and the equivalent input offset voltage is 3.6uV;The equivalent input noise of the auto-zero amplifier at 10 Hz is 13.8nV/sqrt(Hz),and the equivalent input offset voltage is 138.2uV.The above indicators prove that the amplifier has low noise and low offset characteristics and meets the expected goals.