Patent ID: 8477159

Claim:
An offset cancel output circuit of a source driver to which a gray scale voltage corresponding to a gray scale represented by digital data is applied to output a drive voltage to a liquid crystal display panel, the offset cancel output circuit comprising: an operational amplifier with a reference voltage applied to a non-inverted input port thereof; an input capacitor and an output capacitor with each one end thereof connected to an inverted input port of the operational amplifier; and a switching element circuit that has a first field effect transistor connected between the inverted input port and an output port of the operational amplifier, wherein the switching element circuit turns ON the first field effect transistor during a reset operation to make a short circuit between the inverted input port and the output port of the operational amplifier and to allow each of the input capacitor and the output capacitor to accumulate an offset voltage, and wherein during a normal output operation after the reset operation, the switching element circuit turns OFF the first field effect transistor, applies the gray scale voltage to the other end of the input capacitor, and connects the other end of the output capacitor to the output port of the operational amplifier, and wherein during the reset operation and the normal output operation, the switching element circuit applies a first potential equal to the reference voltage to a substrate of the first field effect transistor, and when switching the gray scale voltage during the normal output operation, the switching element circuit applies to the substrate a second potential different from the first potential instead of the first potential so as to prevent a leakage current from flowing to the substrate from a source or a drain of the first field effect transistor.