  Fault tolerance is increasingly being use to design Dependable Digital
Systems (DDS), which refers to the capability of a system to keep performing
its intended functions in existence of faults. DDS are typically used in
Safety-critical system (SCS) such as medical (I&C) devices, Nuclear power
Plants (I&C) devices and Aerospace (I&C) systems, the failure in these systems
can cause harm to environment, death, injury to people. Different fault
tolerance techniques were developed to overcome these issues and that has led
to increase the reliability and dependability of applications on Field
Programmable Gate Arrays (FPGAs). In this paper, multiple related works are
present dealing with different types of faults and fault tolerance methods in
FPGA based systems. Furthermore, a comparison between the evaluation metrics of
previous works of Fault Tolerant (FT) techniques like hardware redundancy
overhead, time delay, reliability, and performance are also present.
