Patent ID: 8149047

Claim:
An operational amplifier of a bandgap reference circuit, comprising: a first NMOS transistor having near zero threshold voltage, a first gate for receiving a first input signal of a pair of differential signals, a first source, and a first drain; a second NMOS transistor having near zero threshold voltage, a second gate for receiving a second input signal of the pair of differential signals, a second source, and a second drain; a third PMOS transistor having a third gate, a third source, and a third drain, wherein the third source is directly coupled to a high voltage source, and the third gate and the third drain are coupled to the first drain; a fourth PMOS transistor having a fourth gate, a fourth source, and a fourth drain, wherein the fourth source is directly coupled to the high voltage source, and the fourth gate is coupled to the first drain and the fourth drain is coupled to the second drain; and a fifth NMOS transistor having a fifth gate, a fifth source, and a fifth drain, wherein the fifth gate receives a bias voltage, the fifth drain is coupled to the first source and the second source, and the fifth source is directly grounded.