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Using a 74LS04 as a latch

2014
30
June

I discovered this by accident today. I never realized a 74LS04 hex inverter could be configured to behave like a 3-port latch by hooking two inverting gates together. Seems pretty obvious and basic right now, but I thought I'd let you guys know anyway.

Here you can see it in action. I'm using a white LED to show the current state of the latch. A jumper wire is used to set the state by switching between GND and Vcc. The LED anode is connected to pin 2, and the cathode to Vcc via a resistor of choice (I happened to use a 2K6). This could be used to reduce component count, or useful if you're short of logic gates.

Or use it as a 3-bit RAM chip. Whatever floats your boat.

The same can also be done with other gates, such as a 7400 NAND, where it is configured as an inverter. And then as a latch.


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