A compressor suitable for use in a portable oxygen concentrator. In one exemplary embodiment, the compressor includes a crankshaft rotatable about a central axis and a plurality of diaphragm assemblies spaced apart around the central axis generally within a plane. The diaphragm assemblies include diaphragms movably mounted to respective housings to at least partially define chambers. A plurality of rods extend between respective diaphragms and the crankshaft. The rods are coupled to the crankshaft such that the rods are offset axially from one another along the central axis and are coupled to the diaphragms for cyclically increasing and decreasing pressure within the chambers as the crankshaft rotates about the central axis.