Development of low noise simulation front-end circuit of IP instrument based on OPA140

The IP method is an important metal prospecting method.However,the IP signal is weak and easily interrupted by electromagnetic signals.Therefore,based on the OPA140 power amplifier chip,the input protection circuit,pre-amplifier,self-potential supplement circuit,low-pass filter,and the circuit transiting from ADC single-ended to double-ended are designed,realizing the development of low noise simulation front-end circuit,improving the ratio of signal and noise.Besides,a dynamic signal analyzer and spectrum analyzer are used to test the response of simulation front-end circuit noise and frequency.TINA-TI software platform simulates and calculates the equivalent input voltage noise of the pre-amplifier,and the test results are consistent with actual needs.The designed simulation front-end circuit is combined with the control panel to make a prototype,which is compared with ELREC 6 direct IP instrument.The results show the parallactic polarizability of the prototype,on the whole,goes with ELREC 6 IP instrument.The prototype can provide a high-quality signal for ADC.The development of low noise simulation front-end circuit meets the design requirements.