Patent ID: 6985030

Claim:
A two-stage amplifier having an offset-compressing function, comprising a prestage differential amplifier and a poststage differential amplifier, the prestage and poststage differential amplifiers being connected in series to each other, wherein: the offset-compressing function compresses an offset voltage of said prestage differential amplifier by increasing the gain of said poststage differential amplifier; the prestage differential amplifier has thereon an in-phase input terminal and an anti-phase input terminal, the 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.