Research On A Low-voltage Low-power Rail-to-rail Operational Amplifier

In CMOS integrated circuits,in addition to area and speed,power consumption is already the third dimension to consider.At the same time,low voltage and low power consumption have also become a design hot spot of analog integrated circuits.Rail-to-rail op amps are widely used due to their wide input and output ranges.How to design a stable rail-to-rail operational amplifier with excellent transconductance and excellent performance under low voltage and low power consumption is the focus of this paper.First of all,on the basis of sufficient investigation,this article deeply understands the research progress of low-voltage and low-power operational amplifiers at home and abroad.Then,establish a 3.3V stable cross-rail to rail operational amplifier research platform to conduct in-depth research on the main modules of the circuit.The input stage designed in this paper is based on the level shift technology,which effectively solves the problem of the limited common-mode input range caused by the constant threshold voltage at low voltage.The bias part of the operational amplifier uses a PTAT reference source.The current generated by the reference source is mirrored to the output branch through current mirror.In the middle stage,the folded cascode structure is adopted to improve the gain of the operational amplifier.It uses a low-voltage wide-swing cascode current mirror structure as a load to increase the output voltage swing of the intermediate stage.The output stage uses a class AB output structure with MOS as the floating voltage source to improve the output efficiency and avoid the cross-over distortion.At the same time,the large driving load capacity is increased.The output stage can also achieve rail-to-rail output swing range.Finally,based on the SMIC 0.18?m CMOS process,the Cadence Virtuoso tool was used to simulate the circuit,and the layout drawing and layout simulation work was completed..The input common mode range of operational amplifier output spring achieve rail-to-rail.And the degree of transconductance change is 0.47% overthe entire common-mode input range.The open-loop gain is 94.8d B while the phase margin is 60.8 °,and unity gain bandwidth is 6.6MHz.The common mode rejection ratio and power supply ratio of the operational amplifier are 117 d B and 124 d B,respectively.The slew rate and settling time of the operational amplifier are 9.3V/?s and 0.41?s,respectively.The power consumption of the operational amplifier is0.52 m W.The effective area of the layout is about 310 × 190?m2.