Negative bias temperature instability (NBTI) is a serious reliability issue for p-channel MOSFETs when stressed with negative gate voltages at high temperatures. There is not any analytical models of NBTI reported so far, which considers the dynamics of NBTI that are commonly observed in experimental data obtained from fast measurement techniques. An analytical model for NBTI is urgently required for circuit simulation purposes. In this paper, we present an analytical solution of switching trap model, which explains the dynamics of negative bias temperature stress. ©2009 IEEE.