Patent ID: 7932740

Claim:
A driving circuit, comprising: a first reference current source, for injecting a reference current; two first switch units, each coupled between the first reference current source and one of a first output port and a second output port; a second reference current source, for sinking the reference current; two second switch units, each coupled between the second reference current source and one of the first output port and the second output port; a load unit, coupled between the first output port and the second output port, wherein a common voltage is applied onto the load unit; and a calibration module, for calibrating an impedance of the load unit according to a voltage at one of the output ports, wherein the voltage is generated due to the reference current passing through one of the two first switch units, the load unit and one of the two second switch units; wherein the calibration module is arranged to compare the voltage at one of the output ports with a predetermined reference voltage to generate a resultant signal, and to calibrate the impedance of the load unit according to the resultant signal; and, the load unit comprises two adjustable resistance elements each coupled between the common voltage and one of the first output port and the second output port; and when the voltage at one of the output ports is located between the first reference current source and the common voltage, the common voltage V cm , the predetermined reference voltage V ref , and the reference current I ref satisfy: V ref =V cm +I ref ×Z; wherein Z is a target impedance of one of the two adjustable resistance elements.