Patent ID: 6859158

Claim:
An analog-digital conversion circuit, comprising: a first circuit having first and second nodes; a selector that selectively applies one of an input analog signal and an analog signal at said second node to said first node; and a control device that controls said selector, said first circuit comprising: a first operational amplifier that amplifies an analog signal from said first node; a first analog-digital converter that converts an analog signal from said first node into a digital signal, the analog signal input to said first operational amplifier being the same as the analog signal input to said first analog-digital converter; a first digital-analog converter that converts the digital signal output from said first analog-digital converter into an analog signal; and a first differential amplifier that amplifies the difference between the analog signal from said first operational amplifier and the analog signal output from said first digital-analog converter and outputs the amplified difference to said second node, said control device controlling said selector so that after the input analog signal is applied to said first node, conversion operation by said first analog-digital converter, conversion operation by said first digital-analog converter, and amplifying operation by said first differential amplifier are carried out for a prescribed number of cycles.