Patent ID: 8294521

Claim:
A power amplifier comprising: a depletion mode high electron mobility transistor (D-mode HEMT) having a gate terminal and a drain terminal, the D-mode HEMT being configured to amplify a signal inputted to the gate terminal and output the amplified signal through the drain terminal without a negative gate bias being applied to the gate terminal; an input matching circuit, having a first inductor configured to serially ground the gate terminal; a DC bias circuit, having a second inductor connected between the drain terminal and a ground, the second inductor being configured to operate as an output matching circuit; and a first DC shielding capacitor connected in series between an input terminal and the gate terminal of the D-mode HEMT so that no transistor is disposed between the D-mode HEMT and the first DC shielding capacitor, wherein a frequency band of the power amplifier is adjusted by varying at least one of the first and second inductors.