Study On A Low Offset Rail-to-rail Input And Output CMOS Operational Amplifier

From the beginning of the world's first transistor invented by Bell Labs in the United States in 1947,semiconductor technology has experienced rapid development.Among them,the development of analog integrated circuits plays an important role in the development of analog integrated circuits.One of the important modules,almost all analog integrated circuits and even some digital integrated circuits also have operational amplifiers.Therefore,operational amplifiers are also called universal integrated circuits.Nowadays,the market for consumer electronics is getting bigger and bigger.In order to reduce power consumption and make standby time longer,the power supply voltage required is lower and lower.Therefore,low power consumption and low power supply voltage are important research directions.At low supply voltages,the study of rail-to-rail op amps is important in order to maximize the input and output signal amplitudes.Firstly,the paper explains the importance of the research of the research object by the development background and history of the op amp.Then introduces the important characteristics of the operational amplifier and the general classification.Based on the theoretical basis of the ordinary operational amplifier,this paper designs a low imbalance.Rail-to-rail input-output CMOS operational amplifiers with input-stages that implement rail-to-rail with a complementary pair of differential pairs,and cross-conduction to achieve constant input-level transconductance across the common-mode input voltage range,Conducive to the design of the frequency compensation module of the op amp;the output stage is a deformation of the AB type structure,which can control the cross-wire type ring structure of the output quiescent current,thus realizing the rail-to-rail of the output stage;the op amp adopts the folded Cascode structure to ensure The high gain of the op amp;the bias current uses a positive temperature coefficient current to ensure that the input stage transconductance does not change with temperature.The offset voltage trimming module uses a digital trimming method to control the current using digital latches and clocks.The mirror array compensates for the magnitude of the current to achieve the low offset of the op amp.Based on the domestic Huahong.35?m CMOS process,the design and simulation of each module and the whole circuit of the circuit are verified by the Cadence Spectre software platform.The final result shows that the input and output voltages can almost reach the rail-to-rail,and the low-frequency gain reaches 110 dB or more.The unity gain bandwidth exceeds 5M,the common mode rejection ratio(CMRR)is above 80 dB,the power supply rejection ratio(PSRR)is about 120 dB,the slew rate is about 6V/?s,the setup time is 0.54?s,and the input offset is about 150?V.Simulation of these parameters.The results are in line with expectations.The op amps designed in this paper can be used in low voltage supply voltages and high precision requirements,such as optical control loops,portable and loop-powered instrumentation,and audio amplification for portable devices.