A minute impedance variation detection device, comprising: a differential amplifier including a first input end, a second input end and an output end; a first impedance having a first end and a second end electrically connected to the first input end of the differential amplifier; a second impedance having a first end and a second end electrically connected to the second input end of the differential amplifier; a sensing electrode electrically connected to the second input end of the differential amplifier for sensing a touch and thus receiving a touch signal; and a signal source electrically connected to the first end of the first impedance and the first end of the second impedance for providing an input signal inputted to the first impedance and the second impedance; and a first capacitor electrically connected to the first input end of the differential amplifier, the first capacitor being a physical capacitor or a parasitic capacitor existing on an integrated circuit pin; wherein the first impedance has an impedance value close to that of the second impedance, and the differential amplifier is based on the input signal and the touch signal to amplify differentially the touch signal and output the differentially amplified touch signal to the output end; wherein the sensing electrode is electrically connected to the second input end of the differential amplifier via an integrated circuit pin having a capacitance value of a first parasitic capacitor; the sensing electrode has a capacitance value of a second parasitic capacitor; the first capacitor has a capacitance value close to that of the first parasitic capacitor and second parasitic capacitor connected in parallel; and wherein the first input end of the differential amplifier is connected only to the second end of the first impedance and the first capacitor. a differential amplifier including a first input end, a second input end and an output end; a first impedance having a first end and a second end electrically connected to the first input end of the differential amplifier; a second impedance having a first end and a second end electrically connected to the second input end of the differential amplifier; a sensing electrode electrically connected to the second input end of the differential amplifier for sensing a touch and thus receiving a touch signal; and a signal source electrically connected to the first end of the first impedance and the first end of the second impedance for providing an input signal inputted to the first impedance and the second impedance; and a first capacitor electrically connected to the first input end of the differential amplifier, the first capacitor being a physical capacitor or a parasitic capacitor existing on an integrated circuit pin; wherein the first impedance has an impedance value close to that of the second impedance, and the differential amplifier is based on the input signal and the touch signal to amplify differentially the touch signal and output the differentially amplified touch signal to the output end; wherein the sensing electrode is electrically connected to the second input end of the differential amplifier via an integrated circuit pin having a capacitance value of a first parasitic capacitor; the sensing electrode has a capacitance value of a second parasitic capacitor; the first capacitor has a capacitance value close to that of the first parasitic capacitor and second parasitic capacitor connected in parallel; and wherein the first input end of the differential amplifier is connected only to the second end of the first impedance and the first capacitor.