Patent ID: 7173490

Claim:
An apparatus for increasing a slew rate of an operational amplifier, comprising: an operational amplifier having an input stage and an output stage, said input stage receiving an input signal, said operational amplifier amplifying said input signal, said output stage outputting an output signal, said output signal being said amplified input signal; a supplementary output device coupled to said output stage of said operational amplifier, said supplementary device being controlled by said output stage; a supplementary input device coupled to said input stage of said operational amplifier, wherein said supplementary input device includes a first sub-current source being controlled by said output stage; and wherein when a voltage level of said output signal is not substantially equal to a voltage level of said input signal, said output stage controls said supplementary output device to provide said output stage with a supplementary output current and controls said supplementary input device to provide said input stage with a supplementary input current; when said voltage level of said output signal is substantially equal to said voltage level of said input signal, said supplementary input device and said supplementary output device is off and do not provide said supplementary input current and said supplementary output current.