What's Inside an FPGA?

Jun 2026

FPGAs (field-programmable gate arrays) are digital programmable ICs that enable engineers to create custom digital circuits simply by writing RTL (register-transfer level) code. FPGAs have proven to be extremely useful in applications that require high-speed digital processing. They have been used for decades in avionics, high-frequency trading, and networking applications.

In engineering, in general it often helps to know something actually works beneath abstractions, such as those afforded to us by hardware description languages (HDLs) such as VHDL and Verilog; as such, this article will explore the digital circuits which make up modern FPGAs.