Research And Design Of A Low Noise CMOS Operational Amplifier

As the most basic and important functional module of analog integrated circuits,CMOS operational amplifiers play an important role in the field of consumer electronics and military electronic systems.In recent years,the development of deep sub-micron technology has been a step-by-step a-nd promising prospect.The voltage of the power supply of integrated circuit systems is getting lower and lower,which seriously deteriorates the signal-to-noise ratio of CMOS operational amplifiers.Therefore,it must be carefully considered in circuit design.The noise performance of the release remains stable.The noise of CMOS op amps mainly includes channel thermal noise and flicker noise.Channel thermal noise can be suppressed by increasing the transconductance and values of the device W/L,which can be suppressed mainly by using a lateral bipolar transistor and DTMOS in a CMOS process.In this paper,a lateral bipolar transistor is used as the differential input pair of the op amp,and a PMOS transistor instead of an NMOS transistor is used as the commongate amplification of the cascode structure,which can effectively improve the noise characteristics of the CMOS op amp.The op amp consists of four parts,which are the bias circuit that provides quiescent current,the lateral bipolar transistor is the differential input stage of the input tube,the diode-connected MOS tube is the common source amplification stage of the load,and the active MOS tube is the load.Power output stage.The low-noise CMOS operational amplifier designed in this paper uses TSMC's 0.18 um CMOS process,the circuit design software is the candidate IC 610,and the simulation software is Spectre.By simulating the designed circuit,the equivalent input noise voltage density when operating at 1HZ is 9.6nV/(?),and the equivalent input noise voltage density at 1KHZ is 7.5nV/(?).This noise performance basically meets the low noise requirements of a CMOS operational amplifier.The op amp's input offset voltage is 14.6uV,the gain bandwidth product is 0.5MHz,and the phase margin is 65°.The above op amp indicators meet the basic requirements of an op amp,which is in line with expectations.