Patent ID: 7639084

Claim:
A power amplifier amplifying an input signal, comprising: a power amplifier circuit having a first transistor of a first type, amplifying the input signal; a bias and compensation circuit having a second transistor of a second type, coupled to the first transistor, generating a DC bias signal to the power amplifier so that the first transistor amplifies the input signal, providing a compensation impedance responsive to the input signal such that a combination of the input impedance and the compensation impedance is substantially constant regardless of the input signal, wherein the first type is different from the second type, the first transistor of the first type is a NMOS transistor, and the second transistor of the second type is a PMOS transistor; the first transistor comprises a first gate receiving the input signal, a first drain coupled to a signal output terminal for outputting the amplified input signal, and a first source coupled to a ground; and the second transistor comprises a second gate coupled to the ground, a second source coupled to the second gate, and a second drain directly connected to the first gate.