NAND Gate (74LS00)

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Building a NAND Gate (74LS00)

If you’ve been following along with the other gate projects (like the NOT, AND, or OR gates), the NAND gate is your next essential stop.
It’s one of the most important logic gates, in fact, every other gate can be built using NANDs alone!

In this post, we’ll wire up a 74LS00 TTL IC, test it using an LED, and see how it behaves in action.

What You’ll Need

  • 1 × 74LS00 IC (Quad 2-input NAND gates)

  • Breadboard + jumper wires

  • 2 × push buttons (or jumper wires for manual input)

  • 2 × 10 kΩ resistors (pull-down resistors)

  • 1 × 330 Ω resistor (for LED current limiting)

  • 1 × LED (any colour)

  • 5 V power supply (or Arduino 5 V pin)

How the NAND Gate Works

A NAND gate is the opposite of an AND gate:
It gives a LOW output only when both inputs are HIGH.

Truth table:


So, the NAND is just “NOT (AND)”.

Inside the 74LS00, there are four separate NAND gates you can use, great for experimenting or combining into bigger logic circuits.

Pinout (74LS00)

Each set of three pins (A, B, F) is one AND gate.

Circuit Diagram

Wiring the Circuit

  1. Place the 74LS00 on your breadboard. Connect pin 14 to +5 V and pin 7 to GND.

  2. Wire two push buttons as your inputs. Connect one button to pin 1, the other to pin 2. The other side of the pushbutton connects to +5V.

  3. Connect between each push button and each pin a 10 kΩ pull-down resistor to GND.

  4. Attach the LED though a 330 Ω resistor from pin 3 (output) to GND.

Now you’re ready to test it.

Understanding It Visually

  • No buttons pressed: both inputs LOW → LED ON

  • Only A pressed: one HIGH, one LOW → LED ON

  • Only B pressed: one HIGH, one LOW → LED ON

  • Both pressed: both HIGH → LED OFF

See the pattern? The LED only turns off when both inputs are HIGH, that’s what makes it a NAND gate.

Where It’s Used

NAND gates are everywhere, they form the backbone of:

  • Memory circuits and flip-flops

  • Digital timers and latches

  • Microprocessor logic (many CPUs are NAND-based)

  • Any place you need universal logic flexibility

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