Do you remember how a NAND gate functions? If not, take a look back at Project NAND gate.

Here's our first "all-electronic" NAND gate circuit that will give you some clues about what goes on in that tiny Quad 2-input NAND IC,

As you build this Project, be sure to set the Select Switch to B. Turn the power ON. Is anything happening with LED 1 ?

Try pressing the Key to see if there's any change. Release the Key and set the Select Switch to A. What does LED 1 do now?

Leave the Select Switch at A and press the Key. Now what does LED 1 do?

From the schematic, you can see what happens when you press the Key and have the Select Switch set to A. The base of the 2SA Transistor has its current flow cut off and the Transistor can no longer operate. And this results in LED 1 going out.

While the NAND gates in the Quad 2-input NAND 7400 IC  are all-electronic, they axe not DTL, They're something called "TTL" - can you figure out what that means?

Take a guess, because we'll find out for sure very soon!






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