Successive approximation type A/D converter

A successive approximation type A/D converter comprising:

• a circuit, connected to one terminal of a first capacitor, for sampling an analog signal input in a sample mode and supplying the sampled analog signal input to said one terminal of said first capacitor;
• a voltage comparator, connected to the other terminal of said first capacitor, for comparing an input terminal voltage in the sample mode with an input terminal voltage in an approximation mode;
• a local D/A converter for generating a local analog signal in the approximation mode in accordance with a successive approximation control digital signal and supplying the local analog signal to said voltage comparator through said first capacitor;
• a successive approximation type control circuit for successively outputting the successive approximation control digital signal in the approximation mode while determining values of bits of an A/D conversion output on the basis of a logic level of an output from said voltage comparator;
• and
• a second capacitor connected between an input terminal of said voltage comparator and a fixed potential terminal having a predetermined voltage, said second capacitor preventing leakage of charge at the input terminal of said voltage comparator to a degree that the input terminal is held at a voltage between and not approximating either of a supplied voltage and said predetermined voltage.