Design Of Bandgap Reference Based On Chopper Modulation And Dynamic Elements Matching Technology

Analog integrated circuits play an irreplaceable role in the integrated circuit industry,and bandgap reference circuits play an important role in analog integrated circuits.The high stability and high precision reference voltage provided by bandgap reference circuits are the guarantee of system stability and accuracy.With the development of technology,the device size decreases.Reduction of device size brings new challenges to circuit design,small mismatch of devices and noise can make circuit performance deteriorate extremely.This is particularly serious for bandgap reference,so it is necessary to design bandgap reference which can improve device mismatch.Firstly,the principle of bandgap reference is analyzed theoretically.On this basis,the main sources of bandgap reference error are analyzed: input offset voltage,noise and device mismatch.Aiming at these error sources,this paper introduces the improvement methods: chopper modulation technology and dynamic element matching technology.The principle of the two techniques is explained in this paper.By modulating the interference to high frequency,the normal signal is kept at low frequency,so as to separate the separation error from the signal,and to improve the bad effects caused by the input offset voltage,noise and device mismatch.In this paper,the Cadence software is used to design the schematic.According to the theoretical knowledge,the classical bandgap reference circuit is designed first,and the design basis and process of the operational amplifier are introduced in detail.The classical bandgap reference is analyzed to determine the source of error.Based on this,the chopper modulation circuit and dynamic element matching circuit are designed.Considering the compensation of the circuit,the position of the chopper modulation circuit and dynamic component matching circuit is determined to ensure the performance of the whole circuit.Based on BiCMOS 0.15 um process,the designed circuit is simulated by Hspice software.The simulation includes functional module simulation and overall circuit simulation.The former simulation verifies that the functions of each module are normal.The latter simulation is to show that chopper modulation circuit and dynamic element matching circuit can improve the error caused by mismatch.So three kinds of circuits are simulated: ideal circuit,mismatch circuit,mismatch circuit with improvement methods.The simulation content is: temperature characteristic,voltage characteristic.The simulation results show that,from the simulation curve,the circuit with mismatch and improvement is closer to the ideal circuit in both trend and amplitude,which seems to be a small translation of the ideal circuit curve,while the trend and amplitude of the error circuit are quite different.From the specific data,the circuit,adding mismatch and improving can improve the error caused by mismatch,the improvement ratio is at least 90%.From the simulation results,it can be seen that the bandgap reference designed in this paper can improve the error caused by the input offset voltage and noise,device mismatch.