NAND Gate – Logic Gates Tutorial

A NAND gate is a logic gate the place the output goes LOW (or “0”) provided that all its inputs are HIGH (or “1”). The schematic image for a NAND gate is just like the AND gate, simply with a circle on the output to point that it’s an inverted model of AND.

NAND truth table and symbol

“NAND” stands for NOT-AND as a result of it’s the identical as an AND gate with a NOT gate on the output.

NAND equivalent by using AND and NOT gates
NAND gate equal utilizing AND and NOT gates

The logic or Boolean expression for a NAND gate is overline{A.B} = Q which signifies that:

If A or B is fake, then Q is true

Reality Desk

NAND gates can have greater than two inputs. However regardless of what number of inputs it has, it’s going to solely give out a LOW or logic “0” if all its inputs are HIGH. As quickly as one of many inputs goes LOW, the output goes HIGH.

2-input NAND Gate Reality Desk

NAND gate symbol
Enter A Enter B Output Q
0 0 1
0 1 1
1 0 1
1 1 0

3-input NAND Gate Reality Desk

3-input NAND gate symbol
Enter A Enter B Enter C Output Q
0 0 0 1
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 1
1 1 0 1
1 1 1 0

Construct a Transistor NAND Gate with RTL

You may construct a NAND gate from transistors and resistors. This system is named resistor-transistor logic (RTL).

RTL version of the NAND gate
NAND gate with transistors and resistors

To get a LOW output, each transistors should be turned on. In any other case, the output shall be pulled HIGH via the highest resistor. Meaning each A and B should be HIGH for the output to grow to be LOW.

Though you might construct it with transistors and resistors, it’s probably not sensible. You’ll want a variety of parts simply to make a easy logic gate. Fortunately, there are various ICs that you should use out-of-the-box.

IC Options with NAND Gates

Pinout for the 4011 IC

If you wish to experiment and construct circuits with NAND gates, you’ll discover them in each the 4000 IC collection and the 7400 IC collection:

  • 4011: 4 2-input NAND gates
  • 4023: Three 3-input NAND gates
  • 4093: 4 2-input NAND gates (Schmitt set off inputs)
  • 4572: One NAND gate (plus a number of different gates)
  • 40107: Two 2-input NAND gates
  • 74HC00: 4 2-input NAND gates (HC is the household, will also be LS/HCT/…)
  • 74HC01: 4 2-input NAND gates (HC is the household, will also be LS/HCT/…)
  • 74HC03: 4 2-input NAND gates (HC is the household, will also be LS/HCT/…)
  • 74HC10: Three 3-input NAND (HC is the household, will also be LS/HCT/…)
  • 74HC11: Three 3-input NAND (HC is the household, will also be LS/HCT/…)

These ought to all be obtainable as hobbyist-friendly through-hole chips. Simply be sure to purchase the DIP bundle model.

NAND Instance Circuit: SR Latch

A typical circuit you possibly can construct with two NAND gates is an SR latch. It is going to bear in mind the final output worth it had, so it’s a easy type of reminiscence.

Within the following circuit, you possibly can flip the Mild-Emitting Diode (LED) on by touching the On pad. The LED will keep on even after you launch the button. To show the LED off, you possibly can press the Off pad.

The contact pads are simply two items of steel that aren’t touching one another. They need to be positioned shut sufficient in order that your finger touches them each when urgent.

Touch switch circuit schematic

Subsequent Step within the Logic Gates Tutorial

Take a look at the opposite articles on this logic gates tutorial:

NOT Gate/Inverter
AND Gate
NAND Gate – (You’re right here)
OR Gate
NOR Gate
XOR Gate

Again to the Logic Gates Overview


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