A compact model in MATLAB environment of amorphous silicon and polycrystalline silicon based thin film transistor is essential to all Active Matrix Organic LED (AMOLED) designers to assessing and envisaging the performance of AMOLED's. This model explains the three regions of thin film transistor operation, i.e. leakage region, sub threshold region and above threshold region. The proposed model shows good settlement with experimental data reported elsewhere. The polycrystalline silicon thin film transistor shows better electrical properties, such as, high relative ON/OFF ratio, high mobility, and low power consumption than amorphous silicon thin film transistor.