Logic Gates And How They Work
Logic gates are the fundamental constructing blocks of digital electronics. These are the parts that we use for “doing stuff” with the 1s and 0s. You possibly can mix them to create different constructing blocks like flip-flops, adders, and extra.
The fundamental logic gates are AND, NAND, OR, NOR, XOR, XNOR, and NOT.
AND gate
The AND gate takes two (or extra) inputs and provides out a 1 (HIGH/true) if all of the inputs are 1. In any other case, it offers out a 0 (LOW/false).
The reality desk is beneath, however all you really want to recollect is that the AND gate wants a 1 on enter A and enter B to provide out 1.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
If you wish to use it in a circuit, the IC 4081 accommodates 4 AND gates.
NOT gate/Inverter
The best logic gate of all is the NOT gate. It takes one bit as enter (A). And it offers as an output (Y) what’s NOT on the enter. So if there’s a 1 on the enter, its output is 0. And if there may be 0 on the enter, its output is 1. It’s additionally referred to as an inverter.
If you wish to use a NOT gate in your circuit, you’ll be able to for instance use the IC 4572 or IC 40106.
OR gate
The OR gate takes two (or extra) inputs and provides out a 1 if any of the inputs are 1. In any other case, it offers out a 0.
The reality desk is beneath, however all you really want to recollect is that the OR gate wants a 1 on enter A or enter B to provide out 1.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
If you wish to use it in a circuit, the IC 4071 accommodates 4 OR gates.
NAND gate
The NAND (or NOT AND) gate operates within the reverse means of the AND gate. It’s like if an AND gate had a NOT gate on its output:
You’ll discover the reality desk beneath. However all you might want to keep in mind is that the one time the output of a NAND gate is 0 is when each the inputs are 1.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
If you wish to use NAND gates in a circuit, the CMOS IC 4011 accommodates 4 NAND gates.
NOR gate
The NOR (or NOT OR) gate operates within the reverse means of the OR gate. It’s as if an OR gate had a NOT gate on its output.
You’ll discover the reality desk beneath. However all you might want to keep in mind is that the one time the output of a NOR gate is 1 is when each the inputs are 0.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
If you wish to use NOR gates in a circuit, the IC 4001 accommodates 4 NOR gates.
XOR gate
The XOR (or Unique OR) gate outputs 1 if one in every of its two inputs is 1 – however not each. It’s also possible to take a look at it on this means – if the 2 inputs are completely different from one another, the output is true.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
If you wish to use XOR gates in a circuit, the IC 4070 accommodates 4 XOR gates.
XNOR gate
The XNOR (or Unique NOT OR) gate works like an XOR gate with an inverter on the output. One other means to take a look at it’s to note that the output turns into 1 if its two inputs are equal – both two 1s or two 0s.
| Enter A | Enter B | Output Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
If you wish to use XNOR gates in a circuit, you’ll discover 4 of them within the IC 4077.
Utilizing Logic Gates in Circuits
A logic gate could be constructed with transistors and often comes as an Built-in Circuit (IC).
There are two traditional IC sequence that comprise numerous the identical capabilities; the 7400-series and the 4000-series.
The 7400-series is the oldest sequence. The 4000-series was launched as a lower-power and extra versatile choice to the 7400. However at the moment, a number of households of the 7400-series exist, some with related properties because the 4000-series.
Take a look at my listing of frequent 4000 sequence IC with pinouts, explanations, and instance circuits for more information.
Full listing of ICs within the 4000-series (Wikipedia)
Full listing of ICs within the 7400-series (Wikipedia)
