Research On Suppression Of DC Bias Voltage In Low-frequency Chopper Amplifier Circuit

With the development of the electronic information age,the level of scientific research continues to progress.The requirements for accuracy,signal-to-noise ratio and other indicators for weak signal detection are also increasing.Among them,the detection of electric and magnetic fields has an irreplaceable role in many fields such as electrical and electronic,space electromagnetic detection,biomedicine,and geological exploration.In order to improve the low frequency weak signal detection index,improve the performance of China’s detection equipment.New challenges are presented to existing technologies.In the detection of low-frequency weak signals,the pre-acquisition circuit is often required to have good performance such as low noise,low offset,and high gain.However,for the current CMOS process,the integrated electronic components often have relatively large low-frequency noise and DC bias voltage,which seriously hinders the subsequent research process.In recent years,great progress has been made in suppressing low frequency noise and improving the performance of the pre-acquisition circuit.The chopper amplifying circuit can perfectly suppress the low-band noise in the circuit,but it contains a severe DC bias voltage component.Therefore,based on the existing chopper amplification circuit,this paper mainly cancels and suppresses the DC bias voltage of the circuit,and optimizes the signal pre-acquisition circuit.The main research work of this paper is as follows:1.Firstly,the existing chopper amplifying circuit is deeply analyzed.The theoretical calculation and the simulation results of time domain and frequency domain are used to illustrate the action of the chopper amplifying circuit on the signal and its principle of suppressing low frequency band noise.Secondly,the correlation analysis of the phenomenon of severe DC bias voltage in the chopper amplifying circuit is carried out,which provides a theoretical basis for the subsequent work.2.In order to optimize the original chopper amplification circuit,a novel low-bias chopper amplification circuit based on negative feedback technology is designed.From the three aspects of theoretical expression calculation,time domain analysis and frequency domain analysis,the circuit’s action on the signal and its principle of canceling the DC bias voltage are analyzed.Secondly,the amplitude-frequency characteristics of the circuit are calculated.It is verified that the circuit has the excellent performance of suppressing the DC bias voltage inherent in the circuit without affecting the transmission signal.3.Based on the previous theoretical calculations and simulation results,we have made the relevant circuits.Firstly,the selection principle of related devices is introduced.Combined with theoretical analysis and actual circuit fabrication,the relevant modules of the circuit(main circuit,feedback circuit,chopping signal generation circuit,power supply circuit)are designed.Finally,the PCB design of the entire circuit was completed.4.Test and verify PCB boards that have been designed and manufactured.The voltage and current noise of the preamplifier circuit,the DC bias voltage of the entire circuit system and the total output noise of the system circuit were tested.Through experimental analysis,the circuit greatly suppresses the DC bias voltage value inherent in the circuit while preserving the low noise level of the chopper amplifier circuit.The experimental results are consistent with the theory and have important significance for improving the low frequency performance of the preamplifier circuit.