Patent ID: 8797098

Claim:
An amplifier, comprising: a first stage comprising: a first transistor coupled at its gate terminal to a first input terminal of the amplifier; a second transistor coupled at its gate terminal to a second input terminal of the amplifier, the first input terminal and the second input terminal comprising a differential voltage input; a first resistor coupled between a drain terminal of the first transistor and a high potential voltage source; a second resistor coupled between a drain terminal of the second transistor and the high potential voltage source; a first current source coupled to a source terminal of the first transistor; a second current source coupled to a source terminal of the second transistor; and a first variable resistor coupled between the source terminal of the first transistor and the source terminal of the second transistor; and a second stage comprising: a third transistor directly coupled at its drain terminal to the drain terminal of the first transistor; a fourth transistor directly coupled at its drain terminal to the drain terminal of the second transistor, coupled at its gate terminal to the drain terminal of the third transistor, and coupled at its drain terminal to a gate terminal of the third transistor; a third current source coupled to a source terminal of the third transistor; a fourth current source coupled to a source terminal of the fourth transistor; and a second variable resistor coupled between the source terminal of the third transistor and the source terminal of the fourth transistor.