Flash a/d converter

A flash A/D converter comprising:

• a reference voltage generator for generating a plurality of reference voltages;
• a first group of amplifiers having a plurality of amplifiers each of which amplifies a difference voltage between each reference voltage generated by the reference voltage generator and a voltage of an input signal;
• and
• a second group of amplifiers having a plurality of amplifiers each of which amplifies voltage obtained by interpolating a portion between output voltages of the amplifiers whose levels of the reference voltage to be inputted are mutually adjacent and a plurality of amplifiers each of which amplifies an output voltage of each amplifier in the first group of amplifiers, wherein;
• each amplifier of the first group of amplifiers is a differential amplifier having a differential pair formed of a plurality of sets of cascode-connected transistors, and has a first switch for short-circuiting respective cascode connection portions of the plurality of transistors configuring the differential pair;
• each amplifier of the second group of amplifiers is a differential amplifier having a differential pair formed of at least two transistors and has a second switch for short-circuiting a portion between input units of the differential pair;
• and
• the first switch and the second switch are controlled to open and close by a control clock of a predetermined period.