Patent ID: 7405622

Claim:
An operational amplifier comprising: an input stage circuit comprising a first differential pair and a second differential pair which are complementary to each other; a first current mirror circuit connected with said first differential pair and configured to function as an active load; a second current mirror circuit connected with said second differential pair and configured to function as an active load; an output stage circuit having a pair of output transistors connected in series between a higher power supply and a lower power supply; an operation point setting circuit configured to set an operation point of said output transistors; and a floating constant current source connected to a first connection node between an input terminal of said first current mirror circuit and said first differential pair, and a second connection node between an input terminal of said second current mirror circuit and said second differential pair, and configured to supply a constant current, wherein said first current mirror circuit and said second current mirror circuit superimpose an output of said input stage circuit on a current corresponding to the constant current by said floating constant current source to supply to said operation point setting circuit.