Patent ID: 7649486

Claim:
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.