Patent ID: 8581171

Claim:
A cyclic A/D converter, comprising: a gain stage including an input receiving an analog signal to be converted to a digital value, an output, and a single end type operational amplifier circuit having a first input, a second input, and output; an A/D converter circuit generating a digital signal including plural bits according to a signal from the output of the gain stage or the analog signal; a logic circuit generating a control signal having first to third values according to the digital signal; and a D/A converter circuit providing the gain stage with at least either one of first and second voltage signals in response to the control signal, wherein the gain stage includes first to third capacitors, the second input of the operational amplifier circuit receives a reference potential, the gain stage performs an operational action generating an operational value with the operational amplifier circuit and the first to third capacitors and a storage action storing the operational value into the first and second capacitors, and the D/A converter circuit has first and second outputs respectively connected to the first and second capacitors, and wherein in the operational action, the third capacitor is connected between the output and the first input of the operational amplifier circuit and also the first and second capacitors are connected between the D/A converter circuit and the first input, and resultantly the operational value is generated at the output of the gain stage, and the D/A converter circuit provides the first output with either of the first and second voltage signals and also includes a switching circuit for providing the second output with either of the first and second voltage signals, in response to the control signal.