Patent ID: 7973605

Claim:
A three-stage frequency-compensated operational amplifier for driving large capacitive loads, comprising: a first-stage circuit for generating a first output signal by amplifying an input signal, comprising: an input end for receiving the input signal; and an output end for outputting the first output signal; a second-stage circuit for generating a second output signal by selectively amplifying the first output signal with a first gain while the first output signal is at a first frequency and amplifying the first output signal with a second gain while the first output signal is at a second frequency, comprising: an input end coupled to the output end of the first-stage circuit for receiving the first output signal; an output end for outputting the second output signal; a bias node which is different from the input end of the second-stage circuit; and a first compensation circuit coupled between the output end and the bias node for modifying the first gain to the second gain at the second frequency; a third-stage circuit for generating a third output signal by amplifying the second output signal, comprising: an input end for receiving the second output signal; and an output end for outputting the third output signal; and a second compensation circuit for adjusting frequency characteristics of the second and third-stage circuits, the second compensation circuit comprising: a first compensation capacitor coupled to the output end of the third-stage circuit.