Provided is a power amplifier including: a depletion mode high electron mobility transistor (D-mode HEMT) configured to amplify a signal inputted to a gate terminal and output the amplified signal through a drain terminal; an input matching circuit configured to serially ground the gate terminal; and a DC bias circuit connected between the drain terminal and a ground. Through the foregoing configuration, the HEMT may be biased only by a single DC bias circuit without any biasing means to provide a negative voltage. Also, superior matching characteristic may be provided in various operation frequency bands through a shunt inductor and a choke inductor.