Patent ID: 7880537
Filing Date: 2011-02-01
Classification: G09G,H03F

Abstract:
1. An offset canceling method of an operational amplifier which has a differential amplifier circuit provided with a pair of input transistors and adjusts currents flowing through the pair of input transistors according to an offset voltage, the operational amplifier being configured to include an output period in which an input signal is amplified and output and a nonoperating period in which an input signal is not amplified, both periods being alternately periodically repeated, the method comprising: storing into a first memory element the output signal of the operational amplifier as a reference voltage, in the output period that is one-cycle preceding; storing into a second memory element a voltage that is the sum of the reference voltage and the offset voltage; and adjusting the currents flowing through the pair of input transistors according to the offset voltage stored in the second memory element, in the output period following storing into the second memory element.