In this paper, a simple and compact Negative Bias Temperature Instability (NBTI) model is proposed. It is based on the reaction-diffusion (tⁿ) and hole-trapping (log(t)) theories. A single shot of DC stress and recovery data is utilized to express duty cycle dependence of NBTI degradation and recovery. Parameter fitting is proceeded by considering that the amount of recovery cannot be larger than stress degradation. The proposed universal model is applied to two types of transistors in different fabrication process technologies, and evaluate its feasibility to show the universality of our proposed model. It replicates stress and recovery successfully with various duty cycles.