NOT Gate (Inverter) – Logic Gates Tutorial

A NOT gate (or inverter) is a logic gate the place the output is the other of the enter. So you possibly can say that the output is NOT the identical because the enter. It’s usually known as an inverter because it inverts the enter.

The schematic image for an inverter is sort of a buffer, simply with a circle on the output to point that it’s an inverted model of the enter.

NOT gate truth table and symbol

The logic or Boolean expression for a NOT gate is overline{A} = Q which signifies that:

Q is the other of A

Fact Desk

A NOT gate can solely have one enter. And its reality desk is fairly easy since there are solely two attainable states; the enter being HIGH (or “1”) or the enter being LOW (or “0”).

NOT Gate Fact Desk

Inverter/NOT gate symbol

Construct an Inverter with Transistor-Resistor Logic

You may construct an inverter/NOT gate from transistors and resistors. This method known as resistor-transistor logic (RTL).

RTL schematic for a NOT gate/inverter
NOT gate with transistors and resistors

If A is HIGH, the transistor activates. When the transistor is turned on, Q is pulled LOW by the transistor. If A is LOW, the transistor is off and Q is pulled HIGH by the resistor as much as VCC.

It’s enjoyable to understand how you may construct it with transistors and resistors. However it’s not likely sensible to make use of that many parts simply to make a easy logic gate. Fortunately, there are numerous ICs which have NOT gates that you should use out-of-the-box.

IC Alternate options with NOT Gates/Inverters

Pinout for the 4001 IC

If you wish to experiment and construct circuits with NOT gates, you’ll discover them in each the 4000 IC sequence and the 7400 IC sequence:

  • 4041: 4 NOT gates/inverters (with buffers)
  • 4049: Six NOT gates/inverters
  • 4069: Six NOT gates/inverters
  • 40106: Six NOT gates/inverters with Schmitt set off
  • 4572: 4 NOT gates/inverters (plus a number of different gates)
  • 74HC04: Six NOT gates/inverters (HC is the household, can be LS/HCT/…)
  • 74HC05: Six NOT gates/inverters (HC is the household, can be LS/HCT/…)
  • 74HC14: Six NOT gates/inverters with Schmitt set off (HC is the household, can be LS/HCT/…)

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

Inverter Instance Circuit: Blinking LED

A enjoyable circuit to construct with inverters is the blinking LED circuit. Within the following circuit, the Mild-Emitting Diode (LED) is blinking repeatedly. Notice that this circuit will solely work with Schmitt set off inverters. So you possibly can construct it for instance with the CD40106B chip or the 74C14 chip.

The resistor R1 and the capacitor C1 units the blinking pace.

Blinking LED circuit using schmitt inverter

Subsequent Step within the Logic Gates Tutorial

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

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

Again to the Logic Gates Overview


Leave a Reply

Your email address will not be published.