Propagation delay
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[edit] Electronics
In electronics, digital circuits and digital electronics, the propagation delay, or gate delay, is the amount of time starting from when the input to a logic gate becomes stable and valid, to the time that the output of that logic gate is stable and valid. Often this refers to the time required for the output to reach 50% of its final output level when the input changes. Reducing gate delays in digital circuits allows them to process data at a faster rate and improve overall performance.
Often one logic gate is connected to another that is connected back to the first. When an invalid input is applied to such a system, the amount of time from when the external inputs to the system become stable and valid to the time the output of both logic gates become stable and valid can be far longer than the normal propagation delay. This is the problem of metastability in electronics.
The principle of logical effort utilizes propagation delays to compare designs implementing the same logical statement.
[edit] Physics
In physics, particularly in the electromagnetism field, the propagation delay is the amount of time it takes for a signal to travel to its destination. For example, in the case of an electric signal, it is the time taken for the signal to travel through a wire. See also, velocity of propagation.
