Patent ID: 7652534

Claim:
A rail-to-rail operational amplifier capable of reducing current consumption comprising: an amplification stage circuit comprising a first compensation output terminal, a second compensation output terminal, a first current output terminal and a second current output terminal, for generating an amplified signal according an input signal of the rail-to-rail operational amplifier; an output stage circuit coupled to the first current output terminal and the second current output terminal of the amplification stage circuit, comprising an output terminal, for outputting the amplified signal; and a compensation circuit coupled to the amplification stage circuit and the output stage circuit, comprising: a first voltage generator for generating a first voltage approximated to a steady state voltage of the first compensation output terminal of the amplification stage circuit; a second voltage generator for generating a second voltage approximated to a steady state voltage of the second compensation output terminal of the amplification stage circuit; a first compensation capacitor comprising a first terminal and a second terminal coupled to the output terminal of the output stage circuit; a second compensation capacitor comprising a first terminal and a second terminal coupled to the output terminal of the output stage circuit; a first switch coupled between the first compensation output terminal and the first terminal of the first compensation capacitor, for selectively coupling the first compensation output terminal to the first terminal of the first compensation capacitor according to a first control signal; a second switch coupled between the first voltage generator and the first terminal of the first compensation capacitor, for selectively coupling the first voltage generator to the first terminal of the first compensation capacitor according to a second control signal; a third switch coupled between the second compensation output terminal and the first terminal of the second compensation capacitor, for selectively coupling the second compensation output terminal to the first terminal of the second compensation capacitor according to a third control signal; and a fourth switch coupled between the second voltage generator and the first terminal of the second compensation capacitor, for selectively coupling the second voltage generator to the first terminal of the second compensation capacitor according to a fourth control signal.