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what are glitches in digital logic circuits

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Dec 20, 2005
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glitches digital logic

Can anybody explain clearly what are glitches and why do they occur in logic circuits?


A glitch happens sometimes as signals propagate through combinational logic.
Before reaching the final steady state value, sometimes, a wrong intermediate value shows up at the output during the settling phase. This is called a glitch.

The reason why it happens is because of the different signal paths have different delays. So when one input reaches the input of a gate while the other input is delayed, the wrong output may occur. The output signal will be corrected once all of the correct input has propagated through.

I've attached a simple diagram.
In the picture below, because of the inverter delay, the AND gate sees both of its input high for a short time. This is when the glitch happens.

for a more detailed description, see below:
**broken link removed**

Good luck!
glitch in digital logic

gleaches are unwanted signals that occur in the circuit

the gleaches can observed in flipflops

gleach will damage the circuit at times.


Suppose you have a combinational logic and if assume having a unit gate delay for each of them, and if the path taken from input to output say, 1st path is having 2 gates and 2nd path is having 2 gates, and if the inputs is given to it, then definitely because of an additional gate in the second path, there exists a glitch in the circuit.

But if you consider the gate has zero delay(unrealistic), then the problem of glitches does not exit

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