Field programmable gate array (FPGA) is one of the most widely used electronics devices. This paper focuses on a study of the FPGA architecture. As a highly structured device, FPGA is constructed by arraying basic elements according to specified rules, so a primary work in designing the FPGA is to determine its architectural parameters. In this paper, we analyze the relationship between some key parameters of a generic FPGA and its performance, and thus present the preferred ranges of these parameters for an optimized FPGA design