LEAP#348 D Latch with NAND gates
The gated D latch is perhaps the fundamental 1-bit memory unit in active digital logic.
There are a few ways of constructing a D latch, here I’m using a NAND gate SR latch as the base, which is convenient as all it requires is a single 74LS00 (quad two-input NAND).
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#347 RF Connectors
Just notes on RF connectors, including crimping your own…
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#346 S/R Latch with NAND Gates
Yet another implementation of a Set-Reset flip-flip, this time using NAND gates.
The NAND gate implementatation has an undefined state with both inputs high, whereas a NOR gate implementatation has an undefined state with both inputs low.
Consequently NOR gates are typically used for active-high SR latches and NAND gates for active-low SR latches. A good example of this is the application in touch sensors, where active low makes sense. See the Boldport Club tap and mostap projects for examples of this.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
Here’s a quick demo:
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LEAP#345 Boldport Club MOSTAP
The MOS TAP circuit was originally published in Elektor magazine in Feb 1975. It was an update or the original TTL Tap circuit to use “state-of-the-art” COSMOS (CMOS) components.
In practical terms, that means 4000-series logic instead of 7400-series logic.
The Boldport Club version of this venerable circuit makes an additional improvement by replacing the output stage BJT drivers with 2N7000 n-channel MOSFETs so that the project really does live up to it’s name!
I’ve added a few mods of my own - a mode switch and a test jig mounted on the beautiful Boldport box (too good to throw away).
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
Here’s a quick demo:
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