A differential amplifier circuit (600A, 600B, 600C, 600D) comprising: a main operational amplifier, the main operational amplifier having a positive output and a negative output, and having a positive input and a negative input; a resistor connecting the positive output to the negative input, and a resistor connecting the negative output to the positive input; wherein the differential amplifier circuit further comprises: a first poly-resistor and a second poly-resistor, one end of the first poly-resistor being connected to the positive output, another end of the first poly-resistor being connected to an inner voltage node, one end of the second poly-resistor being connected to the negative output, another end of the second poly-resistor being connected to the inner voltage node; a controller, the controller being configured to generate a first control voltage and a second control voltage for controlling the first poly-resistor, and to generate a third control voltage and a fourth control voltage for controlling the second poly-resistor; wherein the second control voltage is configured to be different from the first control voltage, and the fourth control voltage is configured to be different from the third control voltage; an auxiliary operational amplifier, wherein the auxiliary operational amplifier is operable to compare an inner voltage at the inner node with a common voltage so as to adjust a DC offset of the main operational amplifier with a negative feedback mechanism. a main operational amplifier, the main operational amplifier having a positive output and a negative output, and having a positive input and a negative input; a resistor connecting the positive output to the negative input, and a resistor connecting the negative output to the positive input; wherein the differential amplifier circuit further comprises: a first poly-resistor and a second poly-resistor, one end of the first poly-resistor being connected to the positive output, another end of the first poly-resistor being connected to an inner voltage node, one end of the second poly-resistor being connected to the negative output, another end of the second poly-resistor being connected to the inner voltage node; a controller, the controller being configured to generate a first control voltage and a second control voltage for controlling the first poly-resistor, and to generate a third control voltage and a fourth control voltage for controlling the second poly-resistor; wherein the second control voltage is configured to be different from the first control voltage, and the fourth control voltage is configured to be different from the third control voltage; an auxiliary operational amplifier, wherein the auxiliary operational amplifier is operable to compare an inner voltage at the inner node with a common voltage so as to adjust a DC offset of the main operational amplifier with a negative feedback mechanism. a first poly-resistor and a second poly-resistor, one end of the first poly-resistor being connected to the positive output, another end of the first poly-resistor being connected to an inner voltage node, one end of the second poly-resistor being connected to the negative output, another end of the second poly-resistor being connected to the inner voltage node; a controller, the controller being configured to generate a first control voltage and a second control voltage for controlling the first poly-resistor, and to generate a third control voltage and a fourth control voltage for controlling the second poly-resistor; wherein the second control voltage is configured to be different from the first control voltage, and the fourth control voltage is configured to be different from the third control voltage; an auxiliary operational amplifier, wherein the auxiliary operational amplifier is operable to compare an inner voltage at the inner node with a common voltage so as to adjust a DC offset of the main operational amplifier with a negative feedback mechanism.