Circuit and method for weak current detection

Abstract

The invention discloses a circuit and a method for weak current detection and belongs to the current detection field. Geminate field effect transistors are employed by an input end to form a difference amplifier, and I-V conversion of a weak current is carried out; a voltage signal after conversion is sent to two sets of proportion operation circuits having symmetric in-phase input modes for proportion operation amplification; difference operation amplification of the voltage signal after proportion operation amplification is carried out, and a difference operation amplification voltage magnitude is measured. According to the method and the device, the junction type geminate field effect transistors are employed to form the difference amplifier as an input level, so input impedance is improved, and the relatively high common-mode inhibition ratio is acquired; the precise proportion operation circuit structures in the symmetric in-phase input modes are employed as the middle level, input impedance is further improved, and measurement precision is improved; the multiple operation amplifier difference amplification detection technology is employed, conflicts of useful-signal weakness and relatively high common-mode interference can be effectively solved, and high gain, high input resistance and the high common-mode inhibition ratio of the detection circuit are realized.

Description

Technical field [0001] The invention belongs to the field of current detection, and specifically relates to a weak current detection circuit and method. Background technique [0002] The existing weak current detection generally uses the current sampling method, that is, the current signal is converted into a voltage sampling signal through a special precision sampling resistor, the voltage sampling signal is compared with the reference voltage, and the feedback control is performed through the operational amplifier to achieve the current Detection function. [0003] As the detection current decreases, the impact of the input impedance of the operational amplifier on the detected current will increase, seriously affecting the current detection accuracy. For cutting-edge products such as semiconductor analyzers, the current detection sensitivity requirements are often as high as nA, or even as high as pA. Using traditional current detection methods, not only the detection accuracy ...

AI Technical Summary

Problems solved by technology

[0003] As the detection current decreases, the influence of the input impedance of the operational amplifier on the detected current will increase, seriously affecting the current detection accuracy

For cutting-edge products such as semiconductor analyzers, the current detection sensitivity requirements are often as high as nA level, or even as high as pA level. The traditional current detection method not only has low detection accuracy, but even cannot perform current detection.

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