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Project Notes

#635 CD4001 SR Latch

Set-Reset latch implemented with CD4001 NOR gates.


Here’s a quick demo..



This circuit is another implementation of a Set-Reset flip-flop, this time using NOR gates. Sometimes this is referred to as a “NOR Latch”. A CD4001 is used to provide the two NOR gates required.

See the LEAP#061 SRLatch circuit for an implementation using BJTs.

Ben Eater has a great video explaining SR latch behaviour:


Truth Table

Set(t) Reset(t) Output Q(t+1)
0 0 no change
0 1 0
1 0 1
1 1 invalid state





Credits and References

About LEAP#635 Digital LogicCMOS/TTL
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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

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Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.