PURPOSE: To attain highly accurate AD converter by adopting a differential type from as an input/output form of a unit circuit, changing alternately an output voltage level of an output terminal in response to the potential difference of input of the unit circuit respectively and connecting the input terminals of the unit circuit in cascade.

CONSTITUTION: In Fig., 19A∼19C are unit circuits. The input and output terminals are made to have a differential form to two terminals each. That is, a threshold voltage is not required except for the 1st stage unit circuit 19A, and since two outputs of the unit circuits 19B, 19C are in complementary voltage relation for the 2nd and succeeding stages, the voltage plays a role of a threshold voltage of other output to each other. Each output voltage is generated from an identical voltage point and complete complementary voltage relation is attained through the symmetricalness of the circuits. Thus, the cascade connection type AD converter is immune to temperature drift appearing as a common mode and noise, the threshold voltage is used in common and the degradation of accuracy due to fluctuation of an output voltage level caused by the decrease in the power supply voltage generated when an output power is formed at each unit circuit is prevented.