The paper reports the realization and characterization of a difference frequency generation spectrometer using periodically poled lithium niobate (PPLN) crystal. The pump and signal laser we used is a Ti:sapphire ring laser and a diode pumped monolithic Nd:YAG laser, respectively. The continuous wave (cw) infrared radiation from 2.8 to 4.8 microm has been generated. The idler radiation can be used to study fundamental absorption bands of molecules and trace gas detection. In this work, we report the detection of nitrous oxide (N(2)O) in atmosphere, the minimum detectable concentration of 10.9 ppbV was achieved using a Herriott cell with the optical path length of 100 m.