Patent ID: 8031159

Claim:
A driving circuit for a liquid crystal display, the driving circuit comprising a plurality of driving units, each of the driving units comprising: a first OP amplifier having a positive input terminal for receiving a first analog signal, a negative input terminal and an output terminal; a second OP amplifier having a positive input terminal for receiving a second analog signal, a negative input terminal and an output terminal; a first switch connected to the output terminal of the first OP amplifier and an output node; a second switch connected to the negative input terminal of the first OP amplifier and the output node; a third switch connected to the output terminal of the second OP amplifier and the output node; and a fourth switch connected to the negative input terminal of the second OP amplifier and the output node; wherein when the driving unit wants to output the first analog signal, the first switch and the second switch are turned on while the third switch and the fourth switch are turned off; and when the driving unit wants to output the second analog signal, the first switch and the second switch are turned off while the third switch and the fourth switch are turned on, wherein an output impedance from the first switch to the first OP amplifier is defined as R out1 =R on1 +R on sw 1/(1 +Aop 1 *B ), and an output impedance from the third switch to the second OP amplifier is defined as R out2 =R on2 +R on sw 3/(1 +Aop 2 *B ), wherein Rout 1 represents the output impedance from the first switch to the first OP amplifier, Rout 2 represents the output impedance from the third switch to the second OP amplifier, Ron 1 represents the output impedance of the first OP amplifier, Ron 2 represents the output impedance of the second OP amplifier, Ronsw 1 represents the impedance of the first switch, Ronsw 3 represent the impedance of the third switch, Aop 1 represent an open-loop gain of the first OP amplifier, Aop 2 represent an open-loop gain of the second OP amplifier, B represents a transfer gain of a feedback loop, wherein the second switch is directly connected to the negative input terminal of the first OP amplifier and the output node.