Patent ID: 6985038

Claim:
An operational amplifier comprising: an operational amplification circuit receiving two input signals and amplifying a difference in voltage between said two input signals to output two signals, respectively; and a feedback circuit receiving said two signals output from said differential amplification circuit to control an amount of an electric current flowing through said differential amplification circuit, said feedback circuit including a voltage setting circuit setting a feedback reference voltage serving as a reference in amplitude for said two signals output, and a common mode feedback circuit receiving said feedback reference voltage set by said voltage setting circuit and said two signals output, and driven thereby to generate a feedback control signal controlling the amount of the electric current flowing through said differential amplification circuit, said voltage setting circuit having a pseudo current path portion forming a current path similar to that passing through said differential amplification circuit, a first voltage setting portion setting as based on a current flowing through said pseudo current path portion a voltage level of a first internal node to be a first voltage corresponding to a voltage level allowing at least one of said two signals output to be maximized in amplitude, a second voltage setting portion setting as based on the current flowing through said pseudo current path portion a voltage level of a second internal node to be a second voltage corresponding to a voltage level allowing at least one of said two signals output to be minimized in amplitude, and an intermediate voltage setting portion setting for a voltage output node an average value of said first and second voltages set in said first and second voltage setting portions for said first and second internal nodes.