FPGA is stand for “Field Programmable Gate Array”, a semiconductor device that can be configured by the customer or designer after manufacturing—hence the name "field-programmable". FPGAs are programmed using a logic circuit diagram or a source code in a hardware description language (HDL) to specify how the chip will work. They can be used to implement any logical function that an application-specific integrated circuit (ASIC) could perform, but the ability to update the functionality after shipping offers advantages for many applications. Xilinx is the first company sold FPGA and it always has the biggest market penetration. Alterna, Lattice, Actel, QuickLogic are companies also sell FPGA. The manufacturers provide diversity of structures and process method on their products. Hence, the choice of structure and suitable process method in order to satisfy requirement of function and stability is very important, that is the key matter in practical systems. The programmable logic device was first invented in the end of 1970s and became popular in semi-conductive industry immediately. Besides ability to be a diversified program, this technology also has small producing time, so it is a very big rival on commerce. Moreover, it is quite easy to design this device and it is reprogrammable.