Patent ID: 9236879
Filing Date: 2016-01-12
CPC Classification: H03M,H04N

Claim Text:
1. A single-ended A/D converter, comprising: a gain stage which includes an input for receiving an analog signal to be converted into a digital value, an output, and an operational amplifier circuit having a first input, a second input and an output; an A/D conversion circuit which refers to a conversion reference voltage and generates a digital signal including one or more bits based on a signal from the output of the gain stage; a logical circuit which generates a control signal according to the digital signal; and a D/A conversion circuit which has first and second outputs, and provides at least a first standard reference voltage or a second standard reference voltage to the gain stage via the first and second outputs in accordance with the control signal, wherein the gain stage includes first to third capacitors, a capacity of the third capacitor is greater than capacities of the first and second capacitors, the second input of the operational amplifier circuit receives a reference potential, the first standard reference voltage is higher than the second standard reference voltage value, the D/A conversion circuit includes a switch circuit for providing either the first or second standard reference voltage to the first output and providing either the first or second standard reference voltage to the second output in response to the control signal, the A/D converter performs a first A/D conversion operation and a second A/D conversion operation, in the first A/D conversion operation, the gain stage performs a first arithmetic operation of generating an operation value with the operational amplifier circuit and the first to third capacitors, and a first storage operation, in the first storage operation, the first capacitor is connected between the input of the gain stage and the second input of the operational amplifier, and stores a first or second standard reference voltage supplied from the first output, or the analog signal, the second capacitor is connected between the second output of the D/A conversion circuit and the second input of the operational amplifier, and stores a first or second standard reference voltage supplied from the second output, the third capacitor is connected between the output and the first input of the operational amplifier circuit, in the first arithmetic operation, when the first or second standard reference voltage is stored in the first capacitor in the first storage operation, the first capacitor is connected between the input to receive the analog signal and the first input, and when the analog signal is stored in the first capacitor in the first storage operation, the first capacitor is connected between the first output and the first input, the second capacitor is connected between the second output and the first input, the operation value is generated in the output of the gain stage by the third capacitor being connected between the output and the first input of the operational amplifier circuit, in the second A/D conversion operation, the gain stage performs a second arithmetic operation of generating an operation value with the operational amplifier circuit and the first to third capacitors, and a second storage operation of storing the operation value in the first and second capacitors, and in the second arithmetic operation, the operation value is generated in the output of the gain stage by the third capacitor being connected between the output and the first input of the operational amplifier circuit, and the first and second capacitors being respectively connected between the first or second output and the first input of the D/A conversion circuit.