Patent ID: 7616146
Filing Date: 2009-11-10
Classification: H03M,H04N

Abstract:
1. An A/D conversion circuit, comprising: an input capacitance, to one end of which an input signal and a reference signal are sequentially applied; an operational amplifier; a first switch that is connected between the other end of the input capacitance and a first input end of the operational amplifier, and is turned on at the time of a signal amplification operation; a feedback capacitance, one end of which is connected to the first input end of the operational amplifier; a second switch that is connected between the other end of the feedback capacitance and an output end of the operational amplifier, and is turned on when an electric charge accumulated in the input capacitance is transferred to the feedback capacitance; a third switch that selectively applies a predetermined voltage to the other end of the feedback capacitance when the input signal is applied to the one end of the input capacitance or at the time of an A/D conversion operation; a fourth switch that, when the input signal is applied to the one end of the input capacitance, selectively causes a short circuit between the first input end and the output end of the operational amplifier; a fifth switch that, when the input signal and the reference signal are applied to the one end of the input capacitance, applies the predetermined voltage to a second input end of the operational amplifier; and a sixth switch that is turned on at the time of the A/D conversion operation to apply a ramp reference voltage to the second input end of the operational amplifier.