Patent ID: 8633771

Claim:
A power amplifier, comprising: an amplifying unit having at least two cascode amplifiers connected in parallel to amplify an input signal; and a bias supply unit supplying bias power to a common gate node of the two cascode amplifiers, and removing a signal of a pre-set frequency band corresponding to a baseband at the common gate node by controlling impedance of the common gate node, wherein the bias supply unit adjusts an impedance of harmonic components of the common gate node according to an inductance component of a bonding wire connected to a ground, wherein the bias supply unit includes first and second resistors dividing a voltage level of the bias power according to a pre-set resistance ratio and a first capacitor connected to be parallel to the first resistor, wherein one end of the first resistor is connected to the ground and the other end thereof is connected to the common gate node, and one end of the second resistor is connected to a bias power terminal to receive the bias power and the other end thereof is connected along with the other end of the first resistor to the common gate node to transfer the divided bias power to the common gate node, wherein the bias supply unit includes a switch connected in series between the other end of the first resistor and the other end of the second resistor, turned on in a high power mode having a pre-set power range, and turned off in a low power mode, having a power range lower than that of the high power mode.