Patent ID: 7557658

Claim:
An amplifier, having a first power supply rail and a second power supply rail, comprising: a first current source coupled to the first power supply rail; an input stage coupled to the first current source, the input stage comprises, a pair of inputs for receiving a pair of differential input signals, and a pair of outputs for delivering a pair of differential intermediate signals in response to the pair of differential input signals; a second current source coupled to the first power supply rail; a summing circuit coupled to the second current source and the pair of outputs from the input stage and operable to sum the output of the input stage, the summing circuit coupled between the first power supply rail and the second power supply rail; a class-AB control circuit having a positive input, a negative input, and a differential output, the class-AB control circuit comprises, a first and a second p-channel transistor, each having a gate, a drain, and a source, the gates of the first and second p-channel transistor coupled together, the source of the first and second p-channel transistor connected to the first power supply rail, a third p-channel transistor, having a gate, a drain and a source, the source coupled to the drain of the first transistor, the gate coupled to the positive input, a fourth p-channel transistor, having a gate, a drain, and a source, the source coupled to the drain of the second transistor, the gate coupled to the gate of the third p-channel transistor to form a first terminal of the differential output, a first n-channel transistor, having a gate, a drain, and a source, the drain coupled to the drain of the fourth p-channel transistor, the source coupled to the second power supply rail, the gate coupled to the negative input to form a second terminal of the differential output, and a second n-channel transistor, having a gate, a drain, and a source, the gate coupled to the drain, the drain coupled to drain of the third p-channel transistor, the source coupled to the second power supply rail; an output stage, having a first input, a second input, and an output, the first and second inputs coupled to the class-AB control circuit, wherein the class-AB control circuit delivers an amplified input signal to the output stage, the output of the output stage delivers current to drive an external load, the output stage comprising a fifth p-channel transistor and a third n-channel transistor.