Combined with the demand of weak signal detection in the electric field meter, the thesis introduced a preamplifier circuit of Atmospheric Electric Field Meter. First it discussed the basic principle structure of the electric field sensor of the field mill. The electric sensor produced the varying electric signal and the paper designed the weak signal detection preamplifier circuit with including IV converter, Differential amplifier and secondary amplifier for the main structure of the circuit. According to the characteristics of atmospheric electric field strength, the paper analyzed and calculated the situation of varying electric signal after through the main part of the circuit. The article used the low bias current of the chips AD795 as a current voltage converter, OP07 and AD620 as the main amplifier circuit. The circuit was tested by multisim, and finally got the useful signal with stability gain, wide range gain and small error.
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