Differential amplifier, two-stage amplifier including the differential amplifier, and analog-to-digital converter including the differential amplifier

An analog-to-digital converter comprising a plurality of amplifying means,

• wherein:
• an input signal is converted into digital form by amplifying differences between an input signal and each of a plurality of different reference signals;
• each of said plurality of amplifying means is a two-stage amplifier comprising a prestage differential amplifier and a poststage differential amplifier which are connected in series to each other, and having an offset-compressing function for compressing an offset voltage of said prestage differential amplifier by increasing the gain of said poststage differential amplifier;
• each prestage differential amplifier has thereon an in-phase input terminal and an anti-phase input terminal;
• each prestage amplifier comprises:
• a first switching unit provided on an input signal line connected to the in-phase input terminal,
• a second switching unit provided on a reference signal line connected to the anti-phase input terminal, and
• a third switching unit provided between the in-phase input terminal and the anti-phase input terminal:
• a difference in potential between the in-phase input terminal and the anti-phase input terminal is differentially amplified by setting said first switching unit and said second switching unit to be on and said third switching unit to be off;
• and
• the in-phase input terminal and the anti-phase input terminal are short-circuited to have a high impedance by setting said first switching unit and said second switching unit to be off and said third switching unit to be on.