NaI(Tl) is one of the oldest and most widely used scintillator due to its high detection efficiency, availability of large size crystal and reasonably good energy resolution. Various studies have been done to study the components contributing to the energy resolution of NaI(Tl) for gamma rays. Apart from components such as statistical contribution of PMT and transfer component, one component is inherent in the scintillator called intrinsic energy resolution. Intrinsic energy resolution presents a fundamental limit to the improvement of energy resolution. In the present work, intrinsic energy resolution of a 2"$\times2$" NaI(Tl) has been measured using advanced data acquisition system PIXIE-4 [3], which is digital pulse processing system and possesses internal amplification. This makes the experimental setup very compact. The measurements were done using $^{\mathbf{137}} {\mathbf{Cs}, } ^{\mathbf{22}}$\textbf{Na and}$^{\mathbf{60}}$ Co gamma ray sources and compared with values reported in literature.
