Automatic test pattern generation automatic test pattern generator is an electronic design automation method used to find an input sequence that, when applied to a digital circuit, enables automatic test equipment to distinguish between the correct circuit behavior and the faulty circuit behavior caused by defects. The designs selected for comparison use LFSR as its core central component around which the entire algorithms are based which contribute in construction of automatic test pattern generator. The LFSR is considered as it gives excellent random characteristics and has a low area overhead which allows it to be placed in the integrated circuit.