Weak current detection device

The invention provides a weak current detection device. The weak current detection device comprises an integrating circuit, a differentiating circuit, a state detection circuit and a discharging circuit. A constant direct current Ix to be measured flows into the reverse input end of the integrating circuit, and the integrating circuit integrates the Ix to obtain a first output voltage V1; the reverse input end of the differentiating circuit is connected with the output end of the integrating circuit, and the differentiating circuit differentiates V1 to obtain second output voltage V2; the input end of the state detection circuit is connected with the reverse input end of the differentiating circuit; the output end of the discharging circuit is connected with the reverse input end of the integrating circuit, and the output current of the discharging circuit is I discharge; the state detection circuit and the discharge circuit cooperate to ensure that the integrating circuit works in a linear region. On one han