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confusion in sequential circuit

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jp619

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sequential circuits are the ones which depend on present and pass input values.... then if an AND gate is given a feedback from its output, does it become a sequential circuit??? justify..
 

In any circuit, if the output is fed back as an input, that circuit can be say as sequential circuit...
But it should have clock pulse..

Deepsss.....
 
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An and gate with feedback (a logic loop) is still a combinational circuit. Sequential circuits need FFs and a clock.
 

please can you elaborate wrt defination of sequential circuit that i have given, that would be really helpful.
 

hi...
Your definition that you have given is not very much correct.. Because, based on the definition "the ones which depend on present and pass input values", the NAND gate which has feedback is sequential circuit.. but.. Clock pulse is the main thing in sequential circuit..... Now are u clear..?

Deepsss...
 

sequential circuits are the ones which depend on present and pass input values....
Click to expand...
This is the defintion that is e.g. given by Enoch in his profound text book Digital Logic and Microprocessor design with VHDL. In so far any logic circuit with feedback, that acts as a state memory must be considered as sequential circuit. Also edge sensitive flip-flops are build from individual logic gates at the gate level.

The classification of logic feedback circuits as sequential hasn't to do with preferred or recommended methods for sequential design. In this respect an asynchronous logic loop would be replaced by a clocked flip-flop construct, that has a simple deterministic timing. I was referring to this menaning of sequential circuits in my first post #3. But thinking about your definition, i see that it's generally correct and applies to any kind of logic with feedback.
 
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    jp619

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By defination its ok ...
But at real time And gate whos in put fed back to its input .
I thinks its little bit tricky ..
Consider

and if its default o/p is zero as most of the IC's have ...
Then it will not wait for the second one its o/p will be zero continuesly
So in this way it depends only on o/p or previous state
look like Sequential CCt
 
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    jp619

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A usable sequential circuit should allow to set a defined state by input signals. A single AND gate actually doesn't. A RS latch formed by two NOR or NAND gates would be a more reasonable example.
 

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