Research And Design Of Low-Power General-Purpose CMOS Operational Amplifier

Operational amplifier is one of the most important functional modules in analog and mixed signal circuit system.It is often used for signal detection,amplification,filtering and so on.For general-purpose operational amplifiers,it is often more challenging to meet more comprehensive application requirements.Despite the rapid development of SOC driven by the progress of CMOS technology,a large number of low-speed,non-standard and niche circuit application scenarios are not suitable for on-chip solutions.Nowadays,more and more mobile devices put forward higher requirements for low-power technology.With the decrease of the power supply voltage,in order to maximize the dynamic range,the operational amplifier needs to be able to process the rail to rail signal.Therefore,the design of a low-power and versatile operational amplifier has become our goal.By studying the development background and key technologies of traditional operational amplifiers,this paper analyzes many technical categories including rail to rail input/output technology,compensation technology and low offset technology,and designs a low-power universal CMOS operational amplifier according to our own needs.The input stage adopts PMOS differential pair based on low ripple charge pump to realize rail to rail input.Compared with traditional technology,the charge pump has more constant transconductance and wider temperature application range.The output stage adopts class AB output stage based on translinear loop,which solves the disadvantage that the current of traditional class AB output stage changes with the power supply voltage.Through simulation,the three frequency compensation technologies of Miller compensation,Cascode compensation and Multipath Zero compensation are compared.After comprehensive consideration,Miller compensation is selected as the compensation mode.Finally,the trimming technology with simple operation and excellent performance is used to reduce the offset voltage.The chip designed in this paper is based on the DB HiTek 180nm process.The final simulation results show that the gain of the low-power general-purpose CMOS operational amplifier designed in this paper can reach 124 dB,the bandwidth is 214 kHz,the common mode rejection ratio is 109 dB and the power supply rejection ratio is 108 dB,the slew rate can reach 269 V/ms,and the settling time is 8.645 μs with a settling accuracy of 0.1%with a power consumption of only 20μA,which meets the design requirements.