PURPOSE: A drive amplifier is provided to drive a high efficient SMPA by providing a signal having wide bandwidth and a high voltage level through a driver amplifier combining an OMD(Optical Modulator Driver) and a buffer amplification unit with an SMPA. CONSTITUTION: A drive amplifier(500) includes an OMD(501) and a buffer amplification unit(502). The OMD firstly amplifies a 1-bit digital bit stream outputted from a DSM(Delta Sigma Modulator). The buffer amplification unit secondly amplifies the firstly amplified 1-bit digital bit stream outputted from the OMD and provides the stream to the SMPA. The buffer amplification unit includes a common source amplifier.
