Successive-approximation type AD converter and pipeline type AD converter

A successive-approximation type AD converter comprising:

• a receiving circuit configured to receive a first analog input signal and to continuously output a second analog input signal according to the first analog input signal;
• a subtraction signal calculation circuit configured to calculate a subtraction signal between an analog reference signal and the second analog input signal in each of n successive conversions (n is a natural number of 2 or more, the same applies hereinafter);
• a determining circuit configured to determine whether a voltage of the subtraction signal is higher than a reference voltage;
• a reference value arithmetic circuit configured to update a reference value so that the analog reference signal approaches the second analog input signal based on a determination result of the determining circuit;
• a DA converter configured to convert the reference value into the analog reference signal;
• and
• an output circuit configured to output a digital output signal based on the determination result of the determining circuit.