Design Of A Rail To Rail Operational Amplifier Based On Gain Boosting Technology

In current society, with the increasing demand of the electronic products, theperformances demand of the product reach a new level. The operational amplifier(OP) works as the entire part of many analog and mixture signal system and italso works as the fundamental unit of the entire system. So it has a bigsignificance on the study of the OP optimization and designing. Electronicproducts could get a degree of improvement in function, volume, powerconsumption as the operational amplifier improved.The MOS devices working principles are introduced in this paper whichfollows the analyzing of the present full differential amplifier circuit structure.The main structure includes two stage type structure, sleeve type structure andfolding type structure, which are compared and analyzed based on theirperformances respectively and the circuit structure are determined in the end. Forfurther increasing the common mode input voltage range and meeting the currentelectronic product performance, the input circuit adopts the rail to rail structure,which increases the input voltage swing margin. The gain boosting technology isintroduced in the amplifier and auxiliary amplifier is used to provide negativefeedback system to the middle level transistor under the condition of the singlestage amplifier, transistor gate voltage is reduced and output impedance isincreased.In this paper, the assisting amplifier is improved based on the traditionalamplifier and the two assisting amplifier in the traditional gain boostingtechnology were combined successfully. The gain boosting technologyapplication were achieved by utilized the single assist operational amplifier,which has the advantages of low amount MOS, low cost and low power.Based on the0.6um CMOS process and simulating tool spectre of Cadence,the design operational amplifier is simulated. And the simulating results showthat the open-loop DC gain is80dB, Phase margin is83°, common mode rejection radio(CMRR) is83dB, power supply rejection radio (PSRR) is98dB,1%setup time is18.9ns, slewing rate is5.5V/μs, which meet the designingrequirements.