Design Of A Current Mirror Structure Immnue To EMI

With the development and application of radio industry and electronic technology,The electromagnetic interference in the environment where electronic equipment stay is becoming more and more serious;Because of the signal processing of analog integrated circuit has entered the stage of high speed,low power consumption and high integration stage,mutual interference between devices in electronic equipment is becoming more and more serious.The current mirror is one of the core modules in the current mode circuit,By improving the anti electromagnetic interference capability of the current mirror,Electromagnetic compatibility of current mode circuits is improved.Compared with voltage mode circuits,current mode circuits have the advantages of high speed,low nonlinear distortion and large dynamic range.Therefore,recently current mode circuits have been used more and more frequently.Current mirror is the basic unit circuit of current mode circuit,Whether the current mirror is good or not is directly related to the normal operation of the current mode circuit.when the electromagnetic interference signal is applied to the basic current mirror,the EMI signal is copied to the output,The device is connected with the output terminal of the current mirror will be affected by electromagnetic interference;Because of the nonlinear characteristics of MOS tube,when the interference signal is superimposed on the DC bias input,the output of the current mirror generates a DC offset,it make the circuit can't work properly.In this paper,the basic principle of the "charge pump" effect is analyzed,and two conditions for the "charge pump" effect are summarized.By using the two measures of decreasing the peak to peak value of the output signal at the output of the current mirror and removing the DC offset caused by the "charge pump",the anti electromagnetic interference capability of the novel current mirror is enhanced.The design process is to analyze the existing current mirror,including basic current mirror,gate filter current mirror,low-pass filter current mirror,DC feedback current mirror and low-pass filter current mirror.The problems that need improvement and optimization are summarized,and a current mirror with stronger electromagnetic interference resistance is designed by using genetic evolution structure.The basic scheme is to optimize the structure of current mirror by using DC feedback structure,low-pass filter structure,current shunt negative feedback structure and cascode negative feedback structure.T-Spice simulation results show that the anti electromagnetic interference current mirror proposed in this paper has better anti electromagnetic interference ability,and the stability has been greatly improved.